JavaScript Reserved Words

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In JavaScript you cannot use these reserved words as variables, labels, or function names:

abstract	arguments	async *	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
function	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
using *	var	void	volatile
while	with	yield

Note

Words marked with* have been added to JavaScript from after 2015.

You can read more the newest JavaScript versions in JS News 2025-2015.

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Removed Reserved Words

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

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JavaScript Objects, Properties, and Methods

You should also avoid using the name of JavaScript built-in objects, properties, and methods:

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Java Reserved Words

JavaScript is often used together with Java. You should avoid using some Java objects and properties as JavaScript identifiers:

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Other Reserved Words

JavaScript can be used as the programming language in many applications.

You should also avoid using the name of HTML and Window objects and properties:

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HTML Event Handlers

In addition you should avoid using the name of all HTML event handlers.

Examples: