B. JavaScript Reserved Words

Reserved words are words that have special meaning to JavaScript. Therefore, they cannot be used as variable or function names.

You'll recognize many of the reserved words from previous chapters, but others will be unfamiliar. Some of the latter group are future reserved words; i.e., it's expected that they'll be commands in future versions of JavaScript. They're being set aside now so that you won't have to revise your code when new revisions are released.

JavaScript reserved words:

These words are part of the JavaScript language as of ECMAScript version 3.

break	for	throw
case	function	try
catch	if	typeof
continue	in	var
default	instanceof	void
delete	new	while
do	return	with
else	switch
finally	this

Additional words reserved for future use by ECMAScript 3:

abstract	final	protected
boolean	float	public
byte	goto	short
char	implements	static
class	import	super
const	int	synchronized
debugger	interface	throws
double	long	TRansient
enum	native	volatile
export	package
extends	private

ECMAScript 4:

As of this writing, ECMAScript version 4 has not been finalized. These words are likely to be added to the reserved words list, so you should avoid using them:

as	namespace	use
false	null
is	TRue

These words are likely to no longer be reserved, but we recommend that you still avoid using them:

boolean	final	short
byte	float	static
char	int
double	long

Other identifiers to avoid:

The object names used in Appendix A aren't officially reserved (outside of the keywords above), but as they are part of the JavaScript language, you shouldn't use them as function or variable names. If you do, abandon all hope; the results will be unpredictable.

In addition, most browsers are case-sensitive, which means that they differentiate between Document and document. Internet Explorer is only sometimes case-sensitive, which means that, for example, it may not understand any difference between Document and document. Consequently, be aware that just because it works in one browser doesn't mean that it'll always work in others. Test, test, test.