JavaScript Reserved Words
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 has 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 |
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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:
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 |
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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 |