Properties

length

Read/write integer specifying the number of elements in the array, or, when the array does not have contiguous elements, a number one larger than the index of the last element in the array. The length property of a new array is initialized when the array is created with the Array() constructor method. Adding new elements to an array created with the Array() constructor updates the length, if necessary:

a = new Array();    a.length initialized to 0
b = new Array(10);  b.length initialized to 10
c = new Array("one", "two", "three");   c.length initialized to 3
c[3] = "four";  c.length updated to 4
c[10] = "blastoff"; c.length becomes 11

You can also set the value of the length property to change the size of an array (i.e., truncate elements or add "undefined" ones).

Methods

join

Converts each of the elements of an array to a string, and then concatenates those strings, inserting the specified separator string between the elements. Returns the resulting string. You can split a string up into array elements--with the split() method of the String object.

array.join()
array.join(separator)   if no separator, the empty string is used

reverse

Reverse, in place (i.e., without creating a new array), the order of the elements of an array.

sort

With no arguments, sorts alphabetically (by character encoding); elements are first converted to strings, if necessary, so that they can be compared. To sort the array elements in some other order, you must supply a function that compares two values and returns a number indicating their relative order.

array.sort()
array.sort(orderfunc)   orderfunc - optional comparison function

The comparison function should take two arguments, a and b, and should:

• Return a value less than zero if, according to your sort criteria, a is less than b, and should appear before b in the sorted array.

• Return zero if a and b are equivalent for the purposes of this sort.

• Return a value greater than zero if a is greater than b for the purposes of the sort.

Methods

toString()

Returns true or false, depending on the boolean value represented by the Boolean object.

valueOf()

Returns the boolean value represented by the Boolean object.

Properties

form

Read-only reference to the Form object that contains the specified button object.

name

Set by the name attribute of the HTML <input> tag that creates the button, this read-only string property provides the name of the button.

form.button_name
form.elements['button_name']

type

See the type property of the Element object (Element.type).

value

Set by the value attribute of the HTML <input> tag that creates the button, this read-only string property provides text displayed in the Button object.

Event Handlers

onClick()

Invoked when the button is clicked; defined by the onClick attribute of the HTML <input> tag. Value may be any number of JavaScript statements, separated by semicolons, that are executed when the user clicks the button.

<INPUT TYPE="button" a definition of the handler
       value="button-text"
       onClick="handler-statements">
button.onclick    a reference to the handler
button.onclick()  an explicit invocation of the handler

HTML syntax

A Button object is created with a standard HTML <input> tag, with the addition of the onClick attribute:

<form>
    ...
  <input
    type="button"   specifies that this is a button
    value="label" the text that is to appear within the button;
        specifies the value property
    [ name="name" ]   a name that can later be used to refer to the button;
    specifies the name property
    [ onClick="handler" ] JavaScript statements to be executed
    when the button is clicked
  >
    ...
</form>

Properties

checked

Read/write Boolean property that specifies whether the Checkbox is checked (true) or not (false). Setting the checked property changes the appearance of the Checkbox but does not cause the onclick() event handler to be invoked.

defaultChecked

Read-only Boolean property that represents the Checkbox's initial state. May be specified using the checked attribute in the HTML <input> tag. Can be used to reset a Checkbox to its default state.

form

Read-only reference to the Form object that contains the Checkbox.

name

Read-only string, set by the HTML name attribute, that specifies the name of the Checkbox object (or array of Checkbox objects).

type

See the type property of the Element object (Element.type).

value

Read/write string that specifies the text that is passed to the Web server if the Checkbox is checked when the form is submitted. The initial value of value is specified by the HTML value attribute. If no value attribute is specified, then the default value string is "on."

Event handlers

onclick()

Invoked when the user clicks on a Checkbox; it is defined by the HTML onClick attribute. The value of this attribute may be any number of JavaScript statements, separated by semicolons, which are executed when the user clicks on the Checkbox.

<INPUT type="checkbox"   a definition of the handler
       onClick="handler-statements">
checkbox.onclick  a reference to the handler
checkbox.onclick();   an explicit invocation of the handler

HTML syntax

A Checkbox object is created with a standard HTML <input> tag, with the addition of the new onClick attribute. Multiple Checkbox objects are often created in groups by specifying multiple <input> tags which have the same name attribute.

<form>
    ...
  <input
    type="checkbox" specifies that this is a checkbox
    [ name="name" ]   a name that can later be used to refer to this checkbox
    or to the group of checkboxes with this name;
    specifies the name property
    [ value="value" ] the value returned when this checkbox is selected;
    specifies the value property
    [ checked ] specifies that the checkbox is initially checked
    Specifies the defaultChecked property
    [ onClick="handler" ] JavaScript statements to be executed when the
    Checkbox is clicked
  >
label the HTML text that should appear next to the Checkbox
    ...
</form>

Methods

getDate()

Returns the day of the month of a Date object. Return values are between 1 and 31.

getDay()

Returns the day of the week of a Date object. Return values are between 0 (Sunday) and 6 (Saturday).

getHours()

Returns the hours field of a Date object. Return values are between 0 (midnight) and 23 (11 PM).

getMinutes()

Returns the minutes field of a Date object. Return values are between 0 and 59.

getMonth()

Returns the month field of a Date object. Return values are between 0 (January) and 11 (December).

getSeconds()

Returns the seconds field of a Date object. Return values are between 0 and 59.

getTime()

Returns the internal, millisecond representation of a Date object (i.e., the number of milliseconds between midnight GMT on 1/1/1970 and the specified date).

getTimezoneOffset()

Returns the difference in minutes between this date (in the local time zone) and GMT. Tells you what time zone the JavaScript code is running in. Since getTimezoneOffset is invoked through a Date object, but doesn't reference the Date object, it should actually be its own function.

getYear()

Returns the year field of a Date object. Return value is the year minus 1900 (e.g., 96 for 1996).

parse()

Parses a string representation of a date and returns it in millisecond format.

setDate()

Sets the day of the month field of a Date object.

date.setDate(day_of_month) // day_of_month is 1-31

setHours()

Sets the hour field of a Date object.

date.setHours(hours) //hours is integer betw 0
(midnight) and 23 (11pm)

setMinutes()

Sets the minutes field of a Date object.

date.setMinutes(minutes) //minutes is integer betw 0 and 59

setMonth()

Sets the month field of a Date object.

date.setMonth(month) //month is integer betw 0 (Jan) and 11 (Dec)

setSeconds()

Sets the seconds field of a Date object.

date.setSeconds(seconds) //seconds is integer betw 0 and 59

setTime()

Sets a Date object in the milliseconds between the desired date/time and midnight GMT on January 1, 1970. Representing a date in this millisecond format makes it independent of time zone.

date.setTime(milliseconds)

setYear()

Sets the year field of a Date object.

date.setYear(year)  // year is year minus 1900; e.g. 96 for 1996

toGMTString()

Converts a Date to a string, using the GMT time zone; format of string varies slightly according to platform.

toLocaleString()

Converts a Date to a string, using the local time zone; uses local conventions for data and time formatting.

UTC()

Converts a numeric date and time specification to millisecond format.

Properties

Note that for all attributes to set a color, the value can be one of the standard color names recognized by JavaScript, or an RGB value in six hexadecimal digits (RRGGBB).

alinkColor

String that specifies the color of activated links (i.e., links being selected by user). Can be set directly in the document <head>, or inherited from the alink attribute in the <body>.

anchors[]

An array of Anchor objects, one for each anchor (i.e., hypertext target) in the document.

anchors.length

Read-only integer specifying the number of elements in the anchors[] array.

applets[]

An array of Java objects, one for each <applet> that appears in the document.

applets.length

A read-only integer specifying the number of elements in the applets[] array.

bgColor

String that specifies the background color of the document. Can be set directly at any point in document, or inherited from the bgcolor attribute in the <body>. Buggy in Netscape 2.0.

cookie

A string that is the value of a cookie associated with this document. String property that allows you to read, create, modify, and delete the cookie(s) that apply to the current document. A "cookie" is a small amount of named data stored by the Web browser so that it can use data input on one page in another page, or recall user preferences across Web-browsing sessions.

document.cookie

The read and write values of the cookie property generally differ. In a JavaScript expression, the cookie property returns a string containing all the cookies from the current document, in name=value pairs (separated by semicolons). Use String.indexOf() and String.substring() to determine the value of a particular cookie. Since cookies cannot contain any semicolons, commas, or whitespace, they are commonly encoded using escape() before storing and decoded using unescape() after retrieving.

To associate a cookie value with the current document for the current Web browsing session, set document.cookie to a string of the form name=value. To create a cookie that can last across browser sessions, include an expiration date by setting document.cookie to a string of the form:

name=value; expires=date

date should be a date specification in the format written by Date.toGMTString().

domain

String that specifies the Internet domain which the document is from; used for security purposes.

embeds[]

An array of Java objects, one for each <embed> tag that appears in the document.

embeds.length

Read-only integer that specifies the number of elements in the embeds[] array.

fgColor

String that specifies the default color of document text. Can be set directly in the document <head>, or inherited from the text attribute in the <body>.

forms[]

An array of Form objects, one for each <form> that appears in the document.

forms.length

Read-only integer specifying the number of elements in the forms[] array.

images[]

An array of Image objects, one for each image embedded in the document with the <img> tag.

images.length

The number of elements in the images[] array.

lastModified

Read-only string that contains the (local) date and time at which document was most recently modified (derived from the HTTP header).

linkColor

String that specifies the color of unvisited links. Can be set directly in the document <head>, or inherited from the link attribute in the <body>.

links[]

An array of Link objects, one for each hypertext link in the document.

links.length

Read-only integer specifying the number of elements in the links[] array.

location

Synonym for the URL property. Use URL instead because it is less likely to be confused with the Window.location property.

plugins[]

Synonym for the embeds[] array.

plugins.length

The number of elements in the plugins[] or embeds[] array.

referrer

Read-only string that contains the URL of the document from which the current document was reached.

title

Read-only string that specifies the <title> of the document.

URL

Read-only string that specifies the URL of the document that contained the link that referred to the current document.

vlinkColor

String that specifies the color of visited links. Can be set directly in the document <head>, or inherited from the vlink attribute in the <body>.

Methods

clear()

Clears the window or frame that contains document.

close()

Displays any output to document that has been written but not yet displayed, and closes the output stream.

open()

Opens a stream to document, so that subsequent document.write() calls can append data to the document.

write()

Appends each of its arguments, in order, to document. Numeric values are converted to a string representation; boolean values are appended as either "true" or "false." When invoked in scripts that are run while the document is loading, you can call document.write() to insert dynamically generated HTML text into the document.

document.write(value,...)

When invoked within a <script> tag on an HTML document that is being parsed, arguments are appended at the location of the tag; when invoked on a document that is not being parsed, the document must first be opened with Document.open().

writeln()

Identical to write(), except that it appends a newline character to the output.

Event handlers

The following event handlers are, strictly speaking, properties of Window, not Document:

onload

Invoked when the document is fully loaded. Specified by the onLoad attribute of <body>.

onUnload

Invoked when the document is unloaded. Specified by the onUnload attribute of <body>.

The Document object obtains values for a number of its properties from attributes of the HTML <body> tag. Further, the HTML contents of a document appear within the <body> and </body> tags.

<body
  [ background="imageURL" ]   a background image for the document
  [ BGCOLOR="color" ] a background color for the document
  [ text="color" ]    the foreground color of the document's text
  [ LINK="color" ]    the color for unvisited links
  [ alink="color" ]   the color for activated links
  [ VLINK="color" ]   the color for visited links
  [ onLoad="handler" ]    JavaScript to run when the document is loaded
  [ onUnload="handler" ]  JavaScript to run when the document is unloaded
>
    HTML document contents go here
</body>

Properties

form

Read-only reference to Form object that contains this element.

name

Read-only string (from the HTML name attribute) that specifies the name of this element. The name of a form element is used for two purposes. First, it is used when the form is submitted. Data for each element in the form is usually submitted in the format:

name=value  // name and value are encoded as necessary
for transmission

If a name is not specified for a form element, then the data for that element cannot be meaningfully submitted to a Web server. The second use of the name property is to refer to a form element in JavaScript code.

type

Read-only string property (Netscape 3.0 and later) that specifies the type of the form element. The value depends on the input element:

Object Type	HTML Tag	type Property
Button	<input type=button>	"button"
Checkbox	<input type=checkbox>	"checkbox"
FileUpload	<input type=file>	"file"
Hidden	<input type=hidden>	"hidden"
Password	<input type=password>	"password"
Radio	<input type=radio>	"radio"
Reset	<input type=reset>	"reset"
Select	<select>	"select-one"
Select	<select multiple>	"select-multiple"
Submit	<input type=submit>	"submit"
Text	<input type=text>	"text"
Textarea	<textarea>	"textarea"

value

Read/write string property that specifies the value to be sent to the server for this element when the form is submitted; initial value specified by the HTML value attribute. For Button, Submit, and Reset objects, the value property specifies the text to appear within the button.

Properties

form

Read-only reference to the Form object that contains the FileUpload object.

name

Read-only string, set by the HTML name attribute, that specifies the name of the FileUpload object. This name can also be used to reference the FileUpload object as a property of its form. (For example, if the name property of a FileUpload object in form foo is "info," then foo.info refers to the FileUpload object.)

type

Read-only string that specifies the type of this form element. For FileUpload objects, it has the value "file." Available in Netscape 3.0 and later.

value

Read-only string that specifies the value contained in the input field (which is also the value sent to the server when the form is submitted). In Netscape 2.0, this field is always blank. In 3.0 any filename specified by the user may be read, but the property still may not be set.

Methods

blur()

Removes the keyboard focus from the FileUpload object. Until focus is granted to some other form element, the user's keystrokes may be ignored by all elements. Due to a bug in Netscape 2.0, the blur() method invokes the onblur() event handler.

focus()

Sets the keyboard focus to the FileUpload object. When focus is set, all keystrokes are automatically entered into this object.

Event handlers

onblur()

Defined by the HTML onBlur attribute, the value of which may be any number of JavaScript statements, separated by semicolons; these statements are executed whenever the FileUpload object loses keyboard focus because of a user action. onblur should only be invoked by direct user actions, but a bug in Netscape 2.0 causes it to be invoked by the FileUpload.blur() method.

onchange()

Invoked when the user changes the value in the FileUpload object and moves the keyboard focus elsewhere. This event handler is not invoked for every keystroke in the FileUpload object, but only when the user completes an edit.

onfocus()

Invoked when a user action causes the FileUpload object to gain the keyboard focus.

HTML syntax

A FileUpload object is created with a standard HTML <input> tag, with the addition of optional attributes for event-handlers:

<form ENCtype="multipart/form-data" method=post>   required attributes
    ...
  <input
    type="file" specifies that this is a FileUpload object
    [ name="name" ]   a name that can later be used to refer to this object
    specifies the name property
    [ size=integer ]  how many characters wide the object is
    [ maxlength=integer ] max allowed number of input characters
    [ onBlur="handler" ]  the onblur() event handler
    [ onChange="handler" ]    the onchange() event handler
    [ onFocus="handler" ] the onfocus() event handler
    ...

Properties

action

Read/write string specifying the URL to which the form is to be submitted. Initially specified by the action attribute of the <form> HTML tag.

elements[]

An array of input elements that appear in the form. Each element is a Button, Checkbox, Hidden, Password, Radio, Reset, Select, Submit, Text or Textarea object.

elements.length

The number of items in the elements[] array.

encoding

Read/write string that specifies the encoding method used for form data. Initially specified by the enctype attribute of the <form> HTML tag. The default encoding of "application/x-www-form-urlencoded" is almost always appropriate.

method

Read/write string that specifies the technique for submitting the form. It should have the value "get" or "post". Initially specified by the method attribute.

target

Read/write string that specifies the name of the frame or window in which the results of submitting a form should be displayed. Initially specified by the target attribute. The special names "_top", "_parent", "_self", and "_blank" are also supported for the target property and the target attribute.

Methods

reset()

Resets each of the input elements of the form to their default values.

submit()

Method that submits a form.

Event Handlers

onreset

Invoked just before the elements of the form are reset. Specified by the onReset attribute.

onsubmit

Invoked just before the form is submitted. Specified by the onSubmit attribute of the <form> tag. This event handler allows form entries to be validated before being submitted.

HTML syntax

A Form object is created with a standard HTML <form> tag. JavaScript adds the optional onSubmit event handler attribute to this tag. The form contains any input elements created with the <input> tag between <form> and </form>.

<form
    [ name="form_name" ]  to name the form in JavaScript
    [ target="window_name" ]  the name of the window for responses
    [ action="url" ]  the URL to which the form is submitted
    [ method=(get|post) ]   the method of form submission
    [ enctype="encoding" ]    how the form data is encoded
    [ onSubmit="handler" ]    a handler invoked when form is submitted
>
    form text and <input> tags go here
</form>

Properties

arguments[]

An array of arguments that were passed to the function. Can only be accessed from within the body of a function. Note that the arguments[] property is actually just a reference to the Function object itself. Thus, instead of using function.arguments[i] and function.arguments.length, you can use function[i] and function.length.

arguments.length

The number of elements in the arguments[] array.

caller

A reference to the Function object that invoked this one, or null if the function is invoked at the top level. Can only be accessed from within the body of a function. You can print out the caller for debugging purposes, and you can even invoke that function through the caller property.

prototype

An object which, for constructor functions, defines properties and methods that will be shared by all objects created with that constructor function. Any objects created through a constructor function will "inherit" the properties and methods defined in that prototype.

Methods

toString()

Converts the Function object to a string by returning the function definition (a string of valid JavaScript code).

valueOf()

Returns the function value contained in a Function object. See the Object.valueOf() method.

Usage

Don't confuse the JavaScript getClass() function with the getClass method of all Java objects. Similarly, don't confuse the JavaScript JavaClass object with the Java java.lang.Class class.

Consider the Java rectangle object created with the following line:

var r = new java.awt.Rectangle();

r is a JavaScript variable that holds a JavaObject object. Calling the JavaScript function getClass() returns a JavaClass object that represents the java.awt.Rectangle class:

var c = getClass(r);

You can see that this is so by comparing this JavaClass object to java.awt.Rectangle:

if (c == java.awt.Rectangle) ...

The Java getClass() method is invoked differently and performs an entirely different function:

c = r.getClass();

After executing the above line of code, c is a JavaObject that represents a java.lang.Class object. This java.lang.Class object is a Java object that is a Java representation of the java.awt.Rectangle class. See your Java documentation for details on what you can do with the java.lang.Class class.

To summarize, you can see that the following expression will always evaluate to true for any JavaObject o:

(getClass(o.getClass()) == java.lang.Class)

Properties

form

Read-only reference to the Form object that contains the Hidden object.

name

Read-only string, set by the HTML name attribute, that specifies the name of the Hidden object. This is also the name that can be used to reference the Hidden object as a property of its form.

type

Read-only string that specifies the type of this form element. For Hidden objects, it has the value "hidden." Available in Netscape 3.0 and later.

value

Read/write string, initially set by the HTML value attribute, which specifies arbitrary data to be transmitted to the server when the form is submitted. This data is never visible to the user.

HTML syntax

A Hidden object is created with a standard HTML <input> tag:

<form>
    ...
  <input
    type="hidden"   specifies that this is a Hidden object
    [ name="name" ]   a name that can later be used to refer to this object;
        specifies the name property
    [ value="value" ] the value transmitted when the form is submitted;
        specifies the initial value of the value property
  >
    ...
</form>

Properties

current

Read-only string that specifies the URL of the current document. Only available with data tainting enabled in Netscape 3.0.

length

The number of URLs that are saved in the History object. (Note that the History object does not provide a property that specifies the position of the current URL in the history list, and because there is no method to move to an absolute position in the history list, only methods to move relative to the current position.)

next

Read-only string that specifies the URL of the document after this one in the history list. Only available with data tainting enabled in Netscape 3.0.

previous

Read-only string that specifies the URL of the document before this one in the history list. Only available with data tainting enabled in Netscape 3.0.

Methods

back()

Go backwards to a previously visited URL (if any). Calling this method has the same effect as a user's click on the Netscape Back button; it's also equivalent to:

history.go(-1);

forward()

Go forward to a previously visited URL (if any). Calling this method has the same effect as a user's click on the Netscape Forward button; it's also equivalent to:

history.go(1);

go()

Go to a previously visited URL (if any).

history.go(relative_position);
history.go(target_string);          //* buggy in 2.0 */

The first form of the History.go() method takes an integer argument (positive argument=forward; negative argument=back) and causes the browser to visit the URL that is the specified number of positions distant in the history list maintained by the History object. Thus history.go(-1) is equivalent to history.back() (and produces the same effect as a user click on the Netscape Back button). Similarly, history.go(3) is equivalent to calling history.forward() three times. In the second syntax, the target_string argument is supposed to make the browser revisit the first (i.e., most recent) URL that contains the specified string. Caveat: This form of the method is buggy in Netscape 2.0 and may cause the browser to crash.

toString()

Returns a string of HTML text. When this string is formatted by a browser (i.e., written with document.write()) it displays the browser history as a table of URLs, each with an appropriate hyperlink. Only available with data tainting enabled in Netscape 3.0.

Properties

border

Read-only integer that specifies the width, in pixels, of the border around an image. Its value is set by the border attribute.

complete

Read-only boolean that specifies whether the image is completely loaded yet; if an error occurs or the loading is aborted, the complete property will be set to true.

height

Read-only integer that specifies the height, in pixels, of the image. Its value is set by the height attribute.

hspace

Read-only integer that specifies the amount of extra horizontal space, in pixels, inserted on the left and right of the image. Its value is set by the hspace attribute.

lowsrc

Read/write string that specifies the URL of an alternate image, suitable for display at low resolutions. Its initial value is set by the lowsrc attribute. Setting this property has no immediate effect; however, if src is set, a new image will be loaded, and on low-resolution systems, the current value of lowsrc will be used instead of the newly updated value of src.

name

Read-only string, specified by the HTML name attribute, that gives the name of the image. When an image is given a name with the name attribute, a reference to the image is placed in the image-name property in addition to the document.images[] array. Image objects created with the Image() constructor function do not have names, and cannot have names assigned.

src

Read/write string that specifies the URL of the image to be displayed. Its initial value is set by the src attribute.

vspace

Read-only integer that specifies the amount of extra vertical space, in pixels, inserted above and below the image. Its value is set by the vspace attribute.

width

Read-only integer that specifies the width, in pixels, of the image. Its value is set by the width attribute.

Event handlers

onabort

Invoked if the user aborts the download of an image. Defined by the onAbort attribute, the value of which may be any number of JavaScript statements (separated by semicolons) that will be executed when the user aborts loading.

<img src="url
     onAbort="handler a definition of the handler
     ...>
image.onabort a reference to the handler
image.onabort()   an explicit invocation of the handler

onerror

Invoked if an error occurs while downloading the image. Defined by the onError attribute, the value of which may be any number of JavaScript statements (separated by semicolons) that will be executed when an error occurs during loading.

<img src="url
     onError="handler a definition of the handler
     ...>
image.onerror a reference to the handler
image.onerror()   an explicit invocation of the handler

onload

Invoked when the image successfully finishes loading. Defined by the onLoad attribute, the value of which may be any number of JavaScript statements (separated by semicolons) that will be executed when the image is completely loaded.

<img src="url
     onLoad="handler  a definition of the handler     ...>
image.onload  a reference to the handler
image.onload()    an explicit invocation of the handler

HTML syntax

The Image object is created with a standard HTML <img> tag, with the addition of event handlers. Some <img> attributes have been omitted from the syntax below, because they are not used by or accessible from JavaScript.

<img src="url" the image to display
     width=pixels the width of the image
     height=pixels    the height of the image
     [ name="image-name" ]    a property name for the image
     [ lowsrc="url" ] alternate low-resolution image
     [ border=pixels ]    width of image border
     [ hspace=pixels ]    extra horizontal space around image
     [ vspace=pixels ]    extra vertical space around image
     [ onLoad=handler ]   invoked when image is fully loaded
     [ onError=handler ]  invoked if error in loading
     [ onAbort=handler ]  invoked if user aborts load
>

Properties

length

Read-only integer that specifies the number of elements in the Java array represented by the JavaArray object.

Usage

If java.awt.Polygon is a JavaClass object, you can create a JavaObject representing an instance of the class using:

p = new java.awt.Polygon();

This object p has properties xpoints and ypoints, which are JavaArray objects representing Java arrays of integers. You could initialize the contents of these arrays with JavaScript code like the following:

for(int i = 0; i < p.xpoints.length; i++)
    p.xpoints[i] = Math.round(Math.random()*100);
for(int i = 0; i < p.ypoints.length; i++)
    p.ypoints[i] = Math.round(Math.random()*100);

Usage

java.lang.System is a JavaClass object that represents the java.lang.System class in Java. The following code reads a static field of this class:

var java_console = java.lang.System.out;

Invoke a static method of this class with a line such as:

var version = java.lang.System.getProperty("java.version");

The JavaClass object allows you to create a new Java object like this:

var java_date = new java.lang.Date();

Usage

java.lang is the name of a JavaPackage that contains the JavaClass java.lang.System. This class has the property out, which is a JavaObject. This JavaObject has a property println, which is a method that can be invoked like this:

java.lang.System.out.println("Hello from Java!");

The previous line of code will write a message on the Java console. java.awt.Rectangle is a JavaClass that represents the java.awt.Rectangle class. The following line creates a JavaObject that represents an instance of this class:

var r = new java.awt.Rectangle(0,0,4,5);

Then access the public fields of this JavaObject r using code such as:

var perimeter = 2*r.width + 2*r.height;

Properties

The properties of a JavaPackage object are the names of the JavaPackage objects and JavaClass objects that it contains. These properties will be different for each individual JavaPackage. Note that it is not possible to use the JavaScript for/in loop to iterate over the list of property names of a Package object; consult a Java reference manual, or examine the Java class hierarchy, to determine the packages and classes contained within any given package.

Usage

You can use JavaPackage objects to refer to any Java class. The java.lang.System class, for example, is:

java.lang.System

Or:

Packages.java.lang.System

Similarly, the netscape.javascript.JSObject class is:

Packagestscape.javascript.JSObject

Properties

hash

The hash portion of the HREF URL, including the leading hash (#) mark. This portion specifies the name of an anchor within the object referred to by the URL.

host

The combination of the hostname and port portions of the HREF URL.

hostname

The hostname portion of the HREF URL.

href

The complete URL specified by the HREF property.

pathname

The path portion of the HREF URL.

port

The port portion of the HREF URL.

protocol

The protocol portion of the HREF URL, including the trailing colon.

search

The search or query portion of the HREF URL, including the leading question mark.

target

The name of a Window object (i.e., a frame or a toplevel browser window) in which the HREF URL should be displayed.

Event handlers

The values of the following attributes may be any number of JavaScript statements separated by semicolons.

onclick()

Statements invoked when the user clicks on the link. Defined by the onClick attribute of the HTML <a> or <area> tag that defines the hypertext link. The onclick() event handler is invoked before the browser follows the clicked hypertext link.

<a onClick="handler-statements">    a definition of the handler
link.onclick  a reference to the handler
link.onclick();   an explicit invocation of the handler

onmouseout()

Statements invoked when the user moves the mouse off of the link. Defined by the onMouseOut attribute of the HTML <a> or <area> tag that defines the hypertext link. Available in 3.0 and later.

<a onMouseOut="handler-statements"> a definition of the handler
<area onMouseOut="handler-statements">   another definition
link.onmouseout   a reference to the handler
link.onmouseout();    an explicit invocation of the handler

onmouseover()

Statements invoked when the user moves the mouse over the link. The status property of the current window may be set here. Defined by the onMouseOver attribute of the HTML <A> or <area> tag that defines the hypertext link.

<a onMouseOver="handler-statements">     a definition of the handler
<area onMouseOver="handler-statements">  another definition
link.onmouseover  a reference to the handler
link.onmouseover();   an explicit invocation of the handler

HTML syntax

A Link object is created with standard <a> and </a> tags, with the addition of the onClick, onMouseOver, and onMouseOut event-handler attributes. The HREF attribute is required for all Link objects. If the name attribute is also specified, then an Anchor object is also created:

<A href="url"
    [ name="anchor_tag" ] creates an Anchor object
    [ target="window_name" ]  where the HREF should be displayed
    [ onClick="handler" ] invoked when link is clicked
    [ onMouseOver="handler" ] invoked when mouse is over link
    [ onMouseOut="handler" ]  invoked when mouse leaves link
>
link text or image    the visible part of the link
</A>

In Netscape 3.0 and later, a Link object is also created by each <area> tag within a client-side image map; standard HTML with the addition of event-handler tags:

<MAP name="map_name">
    <area SHAPE="area_shape"
        COORDS=coordinates
        href="url"
        [ target="window_name" ]  where the HREF should be displayed
        [ onClick="handler" ] invoked when area is clicked
        [ onMouseOut="handler" ]  invoked when mouse leaves area
>
 . . .
</MAP>

Properties

The fields of a Location object refer to the various portions of a URL, which has the following general format:

protocol://hostname:port/pathname?search#hash

hash

The hash portion of the URL, including the leading hash mark (#). This portion specifies the name of an anchor within a single HTML file.

location.hash
window.location.hash
document.links[i].hash

host

A combination of the hostname and port portions of the URL.

location.host
window.location.host
document.links[i].host

hostname

The hostname portion of the URL.

location.hostname
window.location.hostname
document.links[i].hostname

href

The complete URL.

location.href
window.location.href
document.links[i].href

pathname

The path portion of the URL.

location.pathname
window.location.pathname
document.links[i].pathname

port

The port portion of the URL.

location.port
window.location.port
document.links[i].port

protocol

The protocol portion of the URL, including the trailing colon.

location.protocol
window.location.protocol
document.links[i].protocol

search

The search or query portion of the URL, including the leading question mark.

location.search
window.location.search
document.links[i].search

Methods

reload()

Reloads the current document from the cache or server. The optional force argument is a boolean that specifies whether the document should be reloaded even if it hasn't been modified; if omitted or false, the method will reload the full page only if it has been changed since it was last loaded.

location.reload()
location.reload(force)

replace()

Replaces the current document with a new one, without generating a new entry in the browser's session history.

location.replace(url)

Properties

description

Read-only English description of the content and encoding of the type.

enabledPlugin

Reference to the Plugin object that supports this MIME type, or null, if no installed and enabled plug-in supports it. If a MIME type is supported by a plug-in, it can be embedded in a Web page with the <embed> tag; otherwise it must be output in some other way.

name

Read-only name of the MIME datatype (e.g., "text/html"). Value of this property can be used as an index into the navigator.mimeTypes[] array.

suffixes

Read-only comma-separated list of the common filename extensions associated with this MIME type (e.g., for "text/html" the suffixes are "html, htm").

Usage

The navigator.mimeTypes[] array may be indexed numerically, or with the name of the desired MIME type (which is the value of the name property). To check which MIME types are supported by the browser, you can loop through each element in the array numerically. Or, if you just want to check whether a specific type is supported, you can write code like the following:

var show_movie = (navigator.mimeTypes["video/mpeg"] != null);

Properties

appCodeName

Read-only string specifying the code name of the browser.

appName

Read-only string specifying the name of the browser.

appVersion

Read-only string specifying version information for the browser.

mimeTypes[]

An array of MimeType objects describing the MIME types recognized and supported by the browser. Added in Netscape 3.0.

mimeTypes.length

The number of elements in the mimeTypes[] array.

plugins[]

An array of Plugin objects describing the installed plugins. Added in Netscape 3.0.

plugins.length

The number of elements in the plugins[] array.

userAgent

Read-only string passed by the browser as the user-agent header in HTTP requests. In Netscape 2.0 and 3.0, this property is the value of navigator.appCodeName followed by a slash and the value of navigator.appVersion (e.g., Mozilla/2.01 (Win16; I). In Microsoft Internet Explorer 3.0b1 running on Windows 95, this property has the value "Mozilla/2.0 (compatible; MSIE 3.0A; Windows 95)".

Methods

javaEnabled()

Tests whether Java is supported and enabled in the current browser.

taintEnabled()

Tests whether the data-tainting security model is supported and enabled in the current browser (true if enabled). Added in Netscape 3.0.

Constants

MAX_value

The largest representable number.

MIN_value

The smallest (i.e., closest to zero, not most negative) number representable in JavaScript.

NaN

Special Not-a-Number value. JavaScript prints the Number.NaN value as NaN. Note that the NaN value always compares unequal to any other number, including itself. Thus, you cannot check for the not-a-number value by comparing to Number.NaN. Use the isNaN() function instead.

NEGATIVE_INFINITY

Special negative infinite value; returned on overflow. JavaScript displays the NEGATIVE_INFINITY value as -Inf. This value behaves mathematically like an infinity.

POSITIVE_INFINITY

Special infinite value; returned on overflow. JavaScript displays the POSITIVE_INFINITY value as Inf. This value behaves mathematically like an infinity.

Methods

toString()

Converts a number to a string, using a specified radix (base).

number.toString(radix)  // radix is an integer between 2 and 16

By contrast, the toString() method of the Number object is a method of each Number object, not of the Number() constructor function. You can use the toString method with a variable that holds a number, even though that value is not actually an object:

value = 1234;
binary_value = n.toString(2);

JavaScript implicitly invokes the Number() constructor to convert the number to a temporary Number object for which the toString() method can be invoked.

Methods

assign()

If defined, used to implement the JavaScript assignment operator (=).

object.assign(value)    // value is the value to be assigned

eval()

Evaluates a string of JavaScript code in the context of the given object. Prior to Netscape 3.0, eval() is a standalone function; in 3.0, it is a method of Object. However, in 2.0 (client-side JavaScript) it behaves as if it were a method of the Window object.

eval(code)    // Netscape 3.0
window.eval(code)   // Netscape 3.0

toString()

If defined, used to convert an object to a string.

valueOf()

Returns the primitive value of the object, if any. For objects of type Object, this method simply returns the object itself. For other object types, such as Number and Boolean, this method returns the primitive value associated with the object. This method was added in Netscape 3.0.

Example

Defining the toString(), method, and also the less frequently used assign() and valueOf() methods of an object, is most efficiently done in a constructor method for your object type, or with the prototype object of your object.

// define a constructor for the Complex object type
function Complex(x,y) { this.x = x; this.y = y; }
// give it a toString() method
Complex.prototype.toString = 
    new Function("return '{' + this.x + ',' + this.y + '}';");
// Create an object of this new Complex type
c = new Complex(2, 2);
// Convert the object to a string, implicitly invoking the
// toString() method, and display the string.
alert("c = " + c);

Properties

defaultSelected

Read-only boolean that specifies whether this option is selected by default. Set by the selected attribute.

index

Read-only integer that specifies the index of this option within the array of options. The first Option object in the array is at index 0 and has its index property set to 0. The second Option has an index of 1, and so on.

selected

Read/write boolean that specifies whether this option is currently selected. Its initial value is specified by the selected attribute. Can be used to test whether a given option is selected; or to select (by setting it to true) or deselect (by setting it to false) a given option. The Select.onchange() event handler is not invoked.

text

The text that describes the option. It is the plain text (not formatted HTML text) that follows the <option> tag. In 2.0, this property is read-only. In 3.0 it is read/write.

value

Read/write string that specifies the value to be passed to the server if this option is selected when the form is submitted. The initial value is specified by the value attribute.

HTML syntax

An Option object is created by an <option> tag within a <select> which is itself within a <form>. Multiple <option> tags typically appear within the <select>.

<form ...>
  <select  ...>
    <option 
        [ value="value" ] the value returned when the form is submitted
        [ selected ] >   specifies whether this option is initially selected
    plain_text_label  the text to display for this option
        ...
  </select>
        ...
</form>

Properties

java

Reference to a JavaPackage object that represents the top node of the java.* package hierarchy.

netscape

Reference to a JavaPackage object that represents the top node of the netscape.* package hierarchy.

sun

Reference to a JavaPackage object that represents the top node of the sun.* package hierarchy.

Properties

form

Read-only reference to the Form object that contains the Password object.

name

Read-only string, set by the HTML name attribute, that specifies the name of the Password object. This is also the name that can be used to reference the Password object as a property of its form.

type

Read-only string that specifies the type of this form element. For Password objects, it has the value "password." Available in Netscape 3.0 and later.

value

Read/write string, initially set by the HTML value attribute. For security, the user's input is not available through this property, and setting this property does not affect the data transmitted with the form.

Methods

blur()

Removes the keyboard focus from the Password object.

focus()

Sets the keyboard focus to the Password object. When focus is set, all keystrokes are automatically entered into this object.

HTML syntax

A Password object is created with a standard HTML <input> tag:

<form>
    ...
  <input
    type="password" specifies that this is a Password object
    [ name="name" ]   a name that can later be used to refer to this object
        specifies the name property
    [ value="default" ]   the default value transmitted when the form is submitted
    [ size=integer ]  how many characters wide the object is
  >
    ...
</form>

Properties

description

Read-only string that contains a human-readable description of the plug-in, specified by the plug-in itself. This property may specify a full product name, information about the vendor and version, and so on.

filename

Read-only string that specifies the name of the disk file that contains the plug-in code.

mimeTypes[]

Read-only array of MimeType objects, one for each MIME type supported by the plug-in.

mimeTypes.length

The number of elements in the mimeTypes[] array.

name

Read-only string that specifies the name of the plug-in. This is generally a much shorter string than description. The value of this property may be used as an index into the navigator.plugins[] array.

Usage

The navigator.plugins[] array may be indexed numerically when you want to loop through the complete list of installed plug-ins, looking for one that meets your needs. The navigator.plugins[] array can also be indexed by plug-in name, however. That is, if you want to check whether a specific plug-in is installed in the user's browser, you might use code like this:

document.write( navigator.plugins("Shockwave") ?
                "<EMBED src="movie.dir' height=100 WIDTH=100>" :
               "You don't have the Shockwave plugin!" );

The name used as an array index with this technique is the same name that appears as the value of the name property.

Properties

checked

Read/write boolean value that specifies whether the button is checked or not; can be examined to determine the button's state, or be set to select or deselect the button. Setting checked changes the appearance of the button, but does not invoke onClick.

defaultChecked

Read-only Boolean that specifies the initial state of the radio button.

form

Read-only reference to the Form object that contains the Radio object.

name

Read-only string, set by the HTML name attribute, that specifies the name of the Radio button.

type

Read-only string that specifies the type of this form element. For Radio objects, it has the value "radio". Available in Netscape 3.0 and later.

value

Read/write string, initially set by the HTML value attribute, which specifies the value passed to the server if the Radio button is selected when the form is submitted. Each Radio object in a group should specify a distinct value.

Event handlers

onClick

Invoked when the Radio button is clicked; allows you to specify JavaScript code to be executed when the button is checked or "un-checked."

<input type="radio"  a definition of the handler
       onClick="handler-statements">
radio.onclick a reference to the handler
radio.onclick();  an explicit invocation of the handler

HTML syntax

A Radio object is created with a standard HTML <input> tag, with the addition of the new onClick attribute. Radio objects are created in groups by specifying multiple <input> tags that have the same name attribute (mandatory if the radio is part of a form that will submit data to a CGI script). Specifying a name attribute sets the name property, and also allows you to refer to the button by name (instead of as a member of the form elements array).

<form>
    ...
  <input
    type="radio"    specifies that this is a radio button
    [ name="name" ]   a name that can later be used to refer to this button
    or to the group of buttons with this name;
    specifies the name property
    [ value="value" ] the value returned when this button is selected;
    specifies the value property
    [ checked ] specifies that the button is initially checked;
    specifies the defaultChecked property
    [ onClick="handler" ] JavaScript statements to be executed 
    when the button is clicked
  >
label the HTML text that should appear next to the button
    ...
</form>

Properties

form

Read-only reference to the Form object that contains the Reset object.

name

Read-only string, set by the HTML name attribute, that specifies the name of the Reset object. This is also the name that can be used to reference the Reset object as a property of its form.

type

Read-only string that specifies the type of this form element. For Reset objects, it has the value "reset." Available in Netscape 3.0 and later.

value

Read-only string, set by the HTML value attribute, that specifies the text to appear in the button. If no value is specified, then (in Netscape) the button will be labelled "Reset" by default.

Event handlers

onclick()

Invoked when the Reset button is clicked. Defined by the onClick attribute of the HTML <input> tag that defines the Reset button. The value of this attribute may be any number of JavaScript statements, separated by semicolons; these statements will be executed when the user clicks on the Reset button. In Netscape 2.0, there is no way for the onclick() event handler to prevent the fields from being reset. However, in 3.0, the event handler may return false to prevent the Reset object from resetting the form.

<input type="reset"  a definition of the handler
       onClick="handler-statements">
reset.onclick a reference to the handler       
reset.onclick();  an explicit invocation of the handler

HTML syntax

A Reset object is created with a standard HTML <input> tag, with the addition of the onClick attribute:

<form>
    ...
  <input
    type="reset"    specifies that this is a Reset button
    [ value="label" ] the text that is to appear within
the button
    specifies the value property.
    [ name="name" ]   a name that can later be used to refer to the button
    specifies the name property
    [ onClick="handler" ] JavaScript statements to be executed
    when the button is clicked
  >
    ...
</form>

Properties

form

Read-only reference to the Form object that contains the Select object.

length

Read-only integer that specifies the number of elements in the options[] array (i.e., the number of options that appear in the Select object).

name

Read-only string, set by the HTML name attribute, that specifies the name of the select object. This is also the name that can be used to reference the Select object as a property of its form.

options[]

An array of Option objects, each of which describes one of the options displayed within the Select object. The options.length property specifies the number of elements in the array, as does the select.length property. See the Option object for further details.

selectedIndex

Read-only (read/write in 3.0) integer that specifies the index of the selected option within the Select object. If the Select object has its multiple attribute set and allows multiple selections, then this property only specifies the index of the first selected item or -1 if none are selected.

type

Read-only string that specifies the type of this form element. For Select objects, it has the value "select-one" or "select-multiple." Available in Netscape 3.0 and later.

Event handlers

onchange()

Invoked when the user selects or deselects an item. Defined by the onChange attribute of the HTML <select> tag that defines the Select object. The value of this attribute may be any number of JavaScript statements, separated by semicolons; these statements will be executed whenever the user selects or deselects an option. Buggy to the point of uselessness in Netscape 2.0.

<select onChange="handler-statements">   a definition of the handler
select.onchange           a reference to the handler       
reset.onchange();     an explicit invocation of the handler

HTML syntax

A Select object is created with a standard HTML <select> tag, with the addition of the new onChange, onBlur, and onFocus event-handler attributes. Options to appear within the Select object are created with the <option> tag:

<form>
    ...
<SELECT
    name="name    name identifying this object; specifies name property
    [ SIZE=integer ]  number of visible options in select object
    [ MULTIPLE ]    multiple options may be selected, if present
    [ onChange="handler" ]    invoked when the selection changes
    [ onBlur="handler" ]  invoked when object loses focus
    [ onFocus="handler" ] invoked when object gains focus
>
<option value="value1" [selected]> option_label1
<option value="value2" [selected]> option_label2
    .
    .  other options here
    .
</select>
   ...
</form>

Properties

length

The number of characters in the string. For any string s, the index of the last character is s.length-1.

prototype

See Function.prototype.

Methods

anchor()

Returns a copy of the string, enclosed within <a name="name"> and </a> HTML tags. The name attribute of the </a> tag is set to the name argument. If the resulting string is appended to an HTML document (with Document.write() for example), it defines an anchor, with a name of name, which can be the target of a hypertext link.

big()

Returns a copy of the string, enclosed between <big> and </big> HTML tags.

blink()

Returns a copy of the string, enclosed between <blink> and </blink> HTML tags.

bold()

Returns a copy of the string, enclosed between <b> and </b> HTML tags.

charAt()

Extracts the nth character from a string. The first character of the string is numbered 0. If n is not between 0 and string.length-1, then this method returns an empty string. Note that JavaScript does not have a character datatype that is distinct from the string type, so the returned character is a string of length 1.

string.charAt(n)     //n is the index of the character to be returned

fixed()

Returns a copy of the string, enclosed between <tt> and </tt> HTML tags.

fontcolor()

Returns a copy of the string, enclosed between <font color="color"> and </font> HTML tags. The color argument is a string specifying the color name or value to be used as the value of the color attribute in the <font> HTML tag. Colors are specified either as one of the standard color names recognized by JavaScript, or as red, green, and blue color values, expressed as six hexadecimal digits (RRGGBB).

string.fontcolor(color)

fontsize()

Returns a copy of the string, enclosed between <font size="size"> and </font> HTML tags. The size argument is an integer between 1 and 7 or a string that begins with a + or - sign followed by a digit between 1 and 7. If an integer is specified, it is an absolute font size specification. If a string is specified, the font specification is relative to the <basefont> size.

string.fontsize(size)

indexOf()

Searches the string for an occurrence of substring. The search begins at position start within string, or at the beginning if no start is specified. start is an integer between 0 and string.length-1. Returns the position of the first occurrence of substring after the start position, or -1 if no occurrence is found.

string.indexOf(substring)   
string.indexOf(substring, start)

italics()

Returns a copy of the string, enclosed between <i> and </i> HTML tags.

lastIndexOf()

Searches the string backwards for an occurrence of substring. The search begins at position start within string, or at the end, if no start is specified. start is an integer between 0 and string.length-1. Returns the position of the first occurrence of substring before the start position, or -1 if no occurrence is found.

string.lastIndex(substring) 
string.lastIndex(substring, start)

link()

Returns a copy of the string, enclosed between <a href="size"> and </a> HTML tags. href specifies the URL target of the hypertext link that is to be added to the string. This string argument specifies the value of the HREF attribute of the <a> HTML tag.

string.link(href)

small()

Returns a copy of the string, enclosed between <small> and </small> HTML tags.

split()

Converts a string to an array of strings, using a specified delimiter character/string at which the string will be split. If no delimiter is specified, then the returned array has only one element, the string itself. Note that the String.split() method is the inverse of the Array.join() method.

string.split()    
string.split(delimiter)

strike()

Returns a copy of the string, enclosed within <strike> and </strike> HTML tags.

sub()

Returns a copy of the string, enclosed within _and HTML tags.

substring()

Extracts a substring of a string. from is a value between 0 and string.length-1. to is an optional integer that is one greater than the position within string of the last character of the desired substring. to must be between 1 and string.length. The character at position from is included in the substring, while the character at position to is not. The returned string contains characters copied from positions from to to-1 of string.

string.substring(from, to)

sup()

Returns a copy of the string, enclosed within ^and HTML tags.

toLowerCase()

Returns a copy of the string, with all characters converted to lowercase.

toUpperCase()

Returns a copy of the string, with all characters converted to uppercase.

valueOf()

Returns the string value contained in the String object; Netscape 3.0 and later. See Object.valueOf().

Usage

A number of the String methods are used for creating HTML:

link_text = "My Home Page".bold();
document.write(link_text.link("http://www.djf.com/~david"));

The code above code embeds the following string into the HTML document that is currently being parsed:

<A href="http://www.djf.com/~david"><B>My Home Page</B></A>

The following code extracts the 3rd through 5th characters of a string and converts them to upper-case letters:

s.substring(2,5).toUpperCase();

Properties

form

Read-only reference to the Form object that contains the Submit object.

name

Read-only string, set by the HTML name attribute, that specifies the name of the Submit object. This is also the name that can be used to reference the Submit object as a property of its form.

type

Read-only string that specifies the type of this form element. For Submit objects, it has the value "submit." Available in Netscape 3.0 and later.

value

Read-only string, set by the HTML value attribute, that specifies the text to appear in the button. If no value is specified, then (in Netscape) the button will be labelled "Submit Query" by default.

Event handlers

onclick()

Invoked when the Submit button is clicked. Defined by the onClick attribute of the HTML <input> tag that defines the Submit button. The value of this attribute may be any number of JavaScript statements, separated by semicolons; these statements will be executed when the user clicks on the Submit button. In Netscape 2.0, there is no way for the onclick() event handler to cancel the submit action; use the Form.onsubmit() event handler to perform input validation and to cancel form submission if necessary.

<input type="submit" a definition of the handler
       onClick="handler-statements">
submit.onclick    a reference to the handler       
submit.onclick(); an explicit invocation of the handler

HTML syntax

A Reset object is created with a standard HTML <input> tag, with the addition of the onClick attribute:

<form>
    ...
  <input
    type="submit"   specifies that this is a Submit button
    [ value="label" ] the text that is to appear within the button;
    specifies the value property
    [ name="name" ]   a name that can later be used to refer to the button;
    specifies the name property
    [ onClick="handler" ] JavaScript statements to be executed when button is clicked
  >
    ...
</form>

Properties

defaultValue

Read-only string that specifies the initial value to appear in the input field. Specified by the value attribute of the <input> tag.

form

Read-only reference to the Form object that contains the Text object.

name

Read-only string, set by the HTML name attribute, that specifies the name of the Text object. This is also the name that can be used to reference the Text object as a property of its form.

type

Read-only string that specifies the type of this form element. For Text objects, it has the value "text." Available in Netscape 3.0 and later.

value

Read/write string that specifies the value contained in the input field (which is also the value sent to the server when the form is submitted). The initial value of this property is specified by the value attribute of the <input> tag.

Methods

blur()

Removes the keyboard focus from the text object. In Netscape 2.0, the blur() method invokes the onblur() event handler of the Text object. This is inconsistent with the behavior of other event handlers, which are only invoked in response to user actions.

focus()

Sets the keyboard focus to the Text object. When focus is set, all keystrokes are automatically entered into this object.

select()

Highlights all the text in the Text object, and enters a special mode so that future input replaces the highlighted text.

Event handlers

The value of the following event handlers may be any number of JavaScript statements, separated by semicolons, which are executed when the handler is invoked.

onblur()

Invoked when a user action causes the Text object to lose the keyboard focus. Defined by the onBlur attribute of the HTML <input> tag that defines the Text object.

<input type="text onblur"    a definition of the handler
       onClick="handler-statements">
text.onblur   a reference to the handler       
text.onblur();    an explicit invocation of the handler

onchange()

Invoked when the user changes the value in the Text object and then "commits" those changes by moving the keyboard focus elsewhere. Defined by the onChange attribute of the HTML <input> tag that defines the Text object. This event handler is not invoked when the value property of a Text object is set by JavaScript.

<input type="text onchange"  a definition of the handler
       onChange="handler-statements">
text.onchange a reference to the handler       
text.onchange();  an explicit invocation of the handler

onfocus()

Invoked when a user action causes the Text object to gain the keyboard focus. Defined by the onFocus attribute of the HTML <input> tag that defines the Text object. Note that the onfocus event handler is not invoked by the Text.focus() method.

<input type="text onfocus"   a definition of the handler
       onFocus="handler-statements">
text.onfocus  a reference to the handler       
text.onfocus();   an explicit invocation of the handler

HTML syntax

A Text object is created with a standard HTML <input> tag, with the addition of optional attributes for event handlers:

<form>
    ...
  <input
    type="text" specifies that this is a Text object
    [ name="name" ]   a name that can later be used to refer to this object;
    specifies the name property
    [ value="default" ]   the default value transmitted when form is submitted;
    specifies the defaultValue property
    [ size=integer ]  how many characters wide the object is
    [ maxlength=integer ] max allowed number of input characters
    [ onBlur="handler" ]  the onblur() event handler
    [ onChange="handler" ]    the onchange() event handler
    [ onFocus="handler" ] the onfocus() event handler
  >
    ...
</form>

Properties

defaultValue

Read-only string that specifies the initial value to appear in the input field. This default value is whatever plain text appears between the <textarea> and </textarea> tags.

form

Read-only reference to the Form object that contains the Textarea object.

name

Read-only string, set by the HTML name attribute, that specifies the name of the Textarea object. This is also the name that can be used to reference the Textarea object as a property of its form.

type

Read-only string that specifies the type of this form element. For Textarea objects, it has the value "textarea." Available in Netscape 3.0 and later.

value

Read/write string that specifies the value contained in the Textarea (which is also the value sent to the server when the form is submitted). The initial value of this property is the same as the defaultValue property.

Methods

blur()

Removes the keyboard focus from the text object.

focus()

Sets the keyboard focus to the Textarea object. When focus is set, all keystrokes are automatically entered into this object.

Event handlers

The value of the following event handlers may be any number of JavaScript statements, separated by semicolons, which are executed when the handler is invoked.

onblur()

Invoked when a user action causes the Textarea object to lose the keyboard focus. Defined by the onBlur attribute of the HTML <textarea> tag that defines the Textarea object. Note that the onblur() event handler is not invoked by the Textarea.blur() method.

<textarea onblur="handler-statements">   a definition of the handler
</textarea>
text.onblur       a reference to the handler       
text.onblur();        an explicit invocation of the handler

onchange()

Invoked when the user changes the value in the Textarea object and then "commits" those changes by moving the keyboard focus elsewhere. Defined by the onChange attribute of the HTML <textarea> tag that defines the Text object. This event handler is not invoked when the value property of a Text object is set by JavaScript.

<textarea onchange="handler-statements">     a definition of the handler
</textarea>
text.onchange     a reference to the handler       
text.onchange();      an explicit invocation of the handler

This event handler is not invoked for every keystroke in the Textarea object, but only when the user completes an edit.

onfocus()

Invoked when a user action causes the Textarea object to gain the keyboard focus. Defined by the onFocus attribute of the HTML <textarea> tag that defines the Textarea object. Note that the onfocus event handler is not invoked by the Text.focus() method.

<textarea onfocus="handler-statements"> a definition of the handler
</textarea>
text.onfocus  a reference to the handler       
text.onfocus();   an explicit invocation of the handler

HTML syntax

A Textarea object is created with standard HTML <textarea> and </textarea> tags, with the addition of optional attributes for event-handlers. Note that the wrap attribute, which specifies how long lines should be handled, has three legal values: off specifies that they should be left as is; virtual specifies that they should be displayed with line breaks but transmitted without; physical specifies that they should be displayed and transmitted with line breaks inserted.

<form>
    ...
  <textarea
    [ name="name" ]   a name that can later be used to refer to this object
    [ rows=integer ]  how many lines tall the object is
    [ cols=integer ]  how many characters wide the object is
    [ wrap=off|virtual|physical ]   how word wrapping is handled
    [ onBlur="handler" ]  the onblur() event handler
    [ onChange="handler" ]    the onchange() event handler
    [ onFocus="handler" ] the onfocus() event handler
  >
    plain_text    The initial text; specifies defaultValue 
  </textarea>
    ...
</form>

Usage

unescape decodes s by finding and replacing character sequences of the form %xx, where xx is two hexadecimal digits. Each such sequence is replaced by the single character represented by the hexadecimal digits in the Latin-1 encoding. Thus, unescape() decodes the string:

Hello%20World%21

to:

Hello World!

Properties

closed

Read-only boolean that specifies whether a window has been closed. Available in Netscape 3.0.

defaultStatus

Read/write string that specifies the default message to appear in the status line.

document

Reference to the Document object contained in the window.

frames[]

An array of the frames contained by this window. The frames.length property contains the number of elements in the frames[] array, as does the window.length property.

window.frames[i]
window.frames.length

history

Reference to the History object for this window.

java

Reference to the JavaPackage object that is the top of the package name hierarchy for the core java.* packages that comprise the Java language. Available in Netscape 3.0.

length

The number of elements in the frames[] array. Same as frames.length. Read-only.

location

Reference to the Location object for this window.

Math

Reference to an object holding various mathematical functions and constants. Available in Netscape 3.0.

name

String that contains the name of the window. The name is optionally specified when the window is created with the open() method. In Netscape 2.0, this property is read-only; in 3.0 and later, it is read/write.

navigator

Reference to the Netscape object that applies to this and all other windows.

netscape

Reference to the JavaPackage object that is the top of the package name hierarchy for the core netscape.* Java packages from Netscape. Available in Netscape 3.0.

opener

Read-only property that refers to the Window object that contained the document that called open() to create this window. Available in Netscape 3.0.

Packages

Reference to the JavaPackage object that represents the top of the Java package name hierarchy. Available in Netscape 3.0.

parent

Reference to the parent window or frame of the current window. Only useful when the current window is a frame rather than a top-level window.

self

Reference to the window itself. A synonym for window.

status

Read/write string that specifies the current contents of the status line.

sun

Reference to the JavaPackage object that is the top of the package name hierarchy for the sun.* Java packages from Sun Microsystems. Available in Netscape 3.0.

top

Reference to the top-level window that contains the current window. Only useful when the current window is a frame rather than a top-level window.

window

Reference to the window itself. A synonym of self.

Methods

alert()

Displays a simple message in a dialog box. The box has an OK button, and is non-modal (i.e., doesn't interrupt program execution).

window.alert(message)

blur()

Takes keyboard focus from the top-level browser window; this sends the window to the background on most platforms.

clearTimeout()

Cancels a pending timeout operation. The timeoutId argument is a value returned by the call to setTimeout() and identifies which block of deferred code to cancel.

window.clearTimeout(timeoutId)

close()

Closes a window.

confirm()

Asks a yes-or-no question using a dialog box. Returns true if the user clicks the OK button, false if the user clicks Cancel.

window.confirm(question)

focus()

Gives the top-level browser window keyboard focus; this brings the window to the front on most platforms.

open()

Looks up an existing window or opens up a new one. Buggy in Netscape 2.0.

window.open([url, [name, [features]]])

If the name argument specifies the name of an existing window, then a reference to that window is returned. The returned window will display the specified url, but the features will be ignored. If the url is the empty string, a blank window is opened. If name does not refer to an existing window, it specifies the name of the new window; name can be used as the value of a target attribute of an <a> or <form> tag to force documents to be displayed in the window. features is a comma-separated list of features to appear in the window; if this argument is empty or not specified, then all features will be present in the window. If features specifies any one feature, then any feature that does not appear in the list will not appear in the window. The string should not contain any whitespace; each element has the form:

feature[=value]

The available features are:

toolbar

the browser toolbar

location

the input field for entering URLs into the browser

directories

directory buttons, such as "What's New" in Netscape

status

the status line the browser menubar

resizable

if this feature is present and not set to no, then the window will not have resize handles around its border

width

must be followed by a value that specifies the width of the window in pixels

height

must be followed by a value that specifies the height of the window in pixels Displays the specified (plain text) message in a dialog box that also contains a text input field and three buttons (OK, Clear, and Cancel). It should ask the user to enter the information you want. The optional default is a string or integer that will initially be displayed in the input field. If the default argument is not passed, or if its value is null, then prompt() displays the string "<undefined>". Pass the empty string ("") to make prompt() display an empty input box.

window.prompt(message)
window.prompt(message, default)

Selecting the Cancel button causes prompt() to return null; OK returns the text value in the input field; Clear erases the field. Scrolls the document displayed in the Window so that the specified x and y coordinates appear in the upper-left corner. scroll(0,0) specifies the top-left corner of the document.

window.scroll(x, y)   // x, y are coords to scroll to

Executes string of JavaScript code after a specified amount of time (delay milliseconds) elapses. Returns an opaque value (a "timeout id") that can be passed to the clearTimeout() method to cancel the execution of code.

window.setTimeout(code, delay)

Event handlers

The value of the following event handlers may be any number of JavaScript statements, separated by semicolons, which are executed when the handler is invoked.

onblur()

Invoked when a top-level window loses focus. Defined by specifying the onBlur attribute of the <body> or <frameset> tags of the document or frameset that occupies the top-level window. May also be defined by assigning a function to the onblur property of the Window object.

<body    a definition of the handler
    [ onBlur="JavaScript statements" ]
              . . .
>              
<frameset    another way to define the handler
    [ onBlur="JavaScript statements" ]
              . . .
>              
window.onblur=handler-func   defining the handler directly
window.onblur()   an explicit invocation of the handler

onerror()

Invoked when a JavaScript error occurs. The default JavaScript error handler displays an error dialog; you can customize this behavior by providing your own onerror() event handler. Define it for a window by setting the onerror property of a Window object to an appropriate function; unlike other event handlers in JavaScript, onerror() cannot be defined in an HTML tag. You register an onerror() event handler like this:

window.onerror="handler-function

Netscape invokes the handler like this:

window.onerror(message, url, line)

message is the error message; url is the URL of the document in which the error occurred; line is the line number at which the error occurred. When the onerror() handler is invoked, it is passed these three arguments to do with as it will. You can turn off error handling for a window by setting the onerror property of the window to null.

onfocus()

Invoked when the top-level window receives focus. Defined by specifying the onFocus attribute of the <body> or <frameset> tags of the document or frameset that occupies the top-level window. May also be defined by assigning a function to the onfocus property of the Window object.

<body    a definition of the handler
    [ onFocus="JavaScript statements" ]
              . . .
>              
<frameset    another way to define the handler
    [ onFocus="JavaScript statements" ]
              . . .
>              
window.onfocus=handler-func  defining the handler directly
window.onfocus()  an explicit invocation of the handler

onLoad()

Invoked when the document (or frameset) is fully loaded. Defined by specifying the onLoad attribute of the <body> or <frameset> tags of that window. May also be read and invoked through the Window object. Buggy in Netscape 2.0.

<body    a definition of the handler
    [ onLoad="JavaScript statements" ]
              . . .
>              
<frameset    another way to define the handler
    [ onLoad="JavaScript statements" ]
              . . .
>              
window.onload=handler-func   defining the handler directly
window.onload()   an explicit invocation of the handler

onUnload()

Invoked when the browser leaves the document or frameset. Defined by specifying the onUnload attribute of the <body> or <frameset> tags of that window. May also be read and invoked through the Window object.

<body    a definition of the handler
    [ onUnload="JavaScript statements" ]
              . . .
>              
<frameset [ rows="row sizes" ] another way to define the handler
          [ cols="column sizes" ]
          [ onUnload="JavaScript statements" ]
              . . .
>              
window.onunload=handler-func    defining the handler directly
window.onunload() an explicit invocation of the handler