[Chapter 2] 2.7 Reserved Words

2.7 Reserved Words

There are a number of "reserved words" in JavaScript. These are words that you cannot (or should not) use as identifiers (such as variable names) in your JavaScript programs. Table 2.2 lists the keywords in JavaScript. These words have special meaning to JavaScript--they are part of the language syntax itself. This means that they should not be used as identifiers. Table 2.3 lists keywords from Java. Although JavaScript does not currently use any of these keywords, it might in future versions; you should avoid using them in your programs. Finally, Table 2.4 lists other identifiers to avoid. While these identifiers are not strictly reserved, they are the names of datatypes, functions, and variables that are predefined by client-side JavaScript; using them may cause unexpected behavior in your programs. Note that since Internet Explorer is not case-sensitive, you should avoid all variations of these identifiers in Table 2.4, whether in lower- or uppercase.

Table 2.2: Reserved JavaScript Keywords
`break`	`false`	`in`	`this`	`void`
`continue`	`for`	`new`	`true`	`while`
`delete`	`function`	`null`	`typeof`	`with`
`else`	`if`	`return`	`var`

Table 2.3: Java Keywords Reserved by JavaScript
`abstract`	`default`	`implements`	`private`	`throw`
`boolean`	`do`	`import`	`protected`	`throws`
`byte`	`double`	`instanceof`	`public`	`transient`
`case`	`extends`	`int`	`short`	`try`
`catch`	`final`	`interface`	`static`
`char`	`finally`	`long`	`super`
`class`	`float`	`native`	`switch`
`const`	`goto`	`package`	`synchronized`

Table 2.4: Other Identifiers to Avoid
`alert`	`escape`	`JavaPackage`	`onunload`	`setTimeout`
`Anchor`	`eval`	`length`	`open`	`status`
`Area`	`FileUpload`	`Link`	`opener`	`String`
`Array`	`focus`	`Location`	`Option`	`Submit`
`assign`	`Form`	`location`	`Packages`	`sun`
`blur`	`Frame`	`Math`	`parent`	`taint`
`Boolean`	`frames`	`MimeType`	`parseFloat`	`Text`
`Button`	`Function`	`name`	`parseInt`	`Textarea`
`Checkbox`	`getClass`	`navigate`	`Password`	`top`
`clearTimeout`	`Hidden`	`Navigator`	`Plugin`	`toString`
`close`	`History`	`navigator`	`prompt`	`unescape`
`closed`	`history`	`netscape`	`prototype`	`untaint`
`confirm`	`Image`	`Number`	`Radio`	`valueOf`
`Date`	`isNaN`	`Object`	`ref`	`Window`
`defaultStatus`	`java`	`onblur`	`Reset`	`window`
`Document`	`JavaArray`	`onerror`	`scroll`
`document`	`JavaClass`	`onfocus`	`Select`
`Element`	`JavaObject`	`onload`	`self`


Identifiers		Variables and Data Types