Curriculum

Course: JavaScript Basic

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JavaScript Basic

JSHome

0/216

JS Versions

0/36

JS Objects

0/15

JS Funtions

0/22

JS Classes

0/3

JS Async

0/10

JS HTML DOM

0/25

JS Browser BOM

0/17

JS Web APIs

0/7

JS AJAX

0/11

JS JSON

0/16

JS vs jQuery

0/4

JS Graphics

0/7

Text lesson

JS Reserved Words

In JavaScript, you cannot use reserved words as variable names, labels, or function names.

abstract	arguments	await*	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

Removed Reserved Words

The following reserved words were removed from the ECMAScript 5/6 standard:

abstract	boolean	byte	char
double	final	float	goto
int	long	native	short
synchronized	throws	transient	volatile

Avoid using these words as variable names, as ECMAScript 5/6 is not fully supported in all browsers.

JavaScript Objects, Properties, and Methods

You should also avoid using the names of JavaScript built-in objects, properties, and methods as variable names.

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

Java Reserved Words

JavaScript is frequently used alongside Java, so it’s best to avoid using Java object and property names as JavaScript identifiers.

getClass	java	JavaArray	javaClass
JavaObject	JavaPackage

Other Reserved Words

JavaScript can be used as the programming language for various applications.

You should also avoid using the names of HTML and Window objects and their properties as identifiers.

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

Additionally, you should avoid using the names of all HTML event handlers as identifiers.

Examples:

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