JavaScript Reserved Words

In JavaScript, some identifiers we are using in statements. These identifiers are known as reserved words. We cannot use Reserved words as function name or variable name because it can cause unexpected results or errors.

JavaScript Standards

• ECMAScript3 (ES3) was released in December 1999.
• ECMAScript4 (ES4) was abandoned.
• ECMAScript5 (ES5) was released in December 2009.
• ECMAScript6 (ES6) was released in June 2015, and is the latest official version of JavaScript.

As time passes, most of all browsers are beginning to support ES5/ES6 standards.

JavaScript Reserved Words List

In all programming language, reserved words cannot be use as variable name, function name or label names. It can cause JavaScript errors.

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

words mark with star(*) are new words in ECMAScript5

Objects, Properties, and Methods

We should also avoid use of JavaScript built-in Objects, properties and method names.

Below are list of built-in Objects, properties and method names.

Array	Date	eval	function	hasOwnProperty
Infinity	isFinite	isNaN	isPrototypeOf	length
Math	NaN	name	Number	Object
prototype	String	toString	undefined	valueOf

Windows Reserved Words

alert	all	anchor	anchors	area
assign	blur	button	checkbox	clearInterval
clearTimeout	clientInformation	close	closed	confirm
constructor	crypto	decodeURI	decodeURIComponent	defaultStatus
document	element	elements	embed	embeds
encodeURI	encodeURIComponent	escape	event	fileUpload
focus	form	forms	frame	innerHeight
innerWidth	layer	layers	link	location
mimeTypes	navigate	navigator	frames	frameRate
hidden	history	image	images	offscreenBuffering
open	opener	option	outerHeight	outerWidth
packages	pageXOffset	pageYOffset	parent	parseFloat
parseInt	password	pkcs11	plugin	prompt
propertyIsEnum	radio	reset	screenX	screenY
scroll	secure	select	self	setInterval
setTimeout	status	submit	taint	text
textarea	top	unescape	untaint	window

HTML Event Handlers

We should also avoid using HTML event attribute names.

onblur	onclick	onerror	onfocus
onkeydown	onkeypress	onkeyup	onmouseover
onload	onmouseup	onmousedown	onsubmit

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