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JavaScript Reserved Words


In JavaScript you cannot use these reserved words as variables, 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



Words marked with* are new in ECMAScript 5 and 6.

You can read more about the different JavaScript versions in the chapter
JS Versions.


Removed Reserved Words
The following reserved words have been removed from the ECMAScript 5/6 standard:




abstract
boolean
byte
char


double
final
float
goto


int
long
native
short


synchronized
throws
transient
volatile




Do not use these words as variables. ECMAScript 5/6 does not have full support
in all browsers.








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



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



getClass
java
JavaArray
javaClass


JavaObject
JavaPackage






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:




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



onblur
onclick
onerror
onfocus


onkeydown
onkeypress
onkeyup
onmouseover


onload
onmouseup
onmousedown
onsubmit















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Reference: https://www.w3schools.com/js/js_reserved.asp