Learning JavaScript tutorial – JavaScript Reserved KeyWords

JavaScript Reserved KeyWords are part of the JavaScript language syntax. JavaScript Reserved KeyWords has special meanings and used to instruct JavaScript interpreter to perform a specific pre define task. JavaScript has some reserved keywords which can not be used as an identifier. Using JavaScript Reserved KeyWords as an identifier for variable names, function names, and loop labels results in error.

Table 1 -JavaScript 1.5 Reserved KeyWords
abstract	boolean	break	byte	case
catch	char	class	const	delete
debugger	default	delete	do	double
else	enum	export	extends	false
final	finally	float	for	function
goto	if	implements	import	in
instanceof	int	interface	long	native
new	null	package	private	protected
public	return	short	static	super
switch	synchronized	this	throw	throws
transient	true	try	typeof	val
var	void	volatile	while	with

Apart from the keyword listed above, there are some reserved keywords. There other words that may have problems under some versions of JavaScript. These keywords are not currently used in JavaScript, but they are reserved by ECMAScript as possible future extensions to the language. Try to avoid there words as a veriable.

Table 2 -JavaScript Potentially Reserved Words
As	Assert	Decimal	Ensure	Exclude
event	get	include	internal	invariant
Is	Namespace	Require	Sbyte	Set
uint	ulong	use	ushort

This list not end here, we are using JavaScript as a Client side scripting language. Mostly we use JavaScript with Server Side Scripting languages like ASP, ASP.NET and PHP. To maintain good compatibility there are some words which we should avoid to use as an identifiers. They are…

Table 3 – Words should avoid to use as an identifier
arguments	Array	Boolean	Date	decodeURI
decodeURIComponent	encodeURI	Error	escape	eval
EvalError	Function	Infinity	isFinite	isNaN
Math	NaN	Number	Object	parseFloat
parseInt	RangeError	ReferenceError	RegExp	String
SyntaxError	TypeError	undefined	unescape	URIError