Description

JavaScript Reserved Keywords are the words that cannot be used as identifiers within a JavaScript code or program.

  • A JavaScript identifier can be a variable name, function name, loop label, etc.,

For backward compatibility, we should better avoid using all the reserved keywords either as variable names or property names in JavaScript code.

Reserved Keywords in ECMAScript 5 (ES5)

The below list contains the keywords that are reserved in ECMAScript 5.

The list also includes keywords "reserved for future" as well as keywords that are "disallowed in strict mode".

arguments enum instanceof switch
break eval interface this
case export let throw
catch extends new true
class false null try
const finally package typeof
continue for private var
debugger function protected void
default if public while
delete implements return with
do import static yield
else in super  

Reserved Keywords in ECMAScript 6 (ES6)

The below list contains the keywords that are reserved in ECMAScript 6.

The list also includes keywords "reserved for future" as well as keywords that are "disallowed in strict mode".

arguments else in super
await enum instanceof switch
break eval interface this
case export let throw
catch extends new true
class false null try
const finally package typeof
continue for private var
debugger function protected void
default if public while
delete implements return with
do import static yield

Future Reserved Keywords

The below list contains the keywords that are "reserved for future" by older specifications, before ECMAScript 5.

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

Overall

We now know the list of all the JavaScript reserved keywords that cannot be used as identifiers within a JavaScript code.

Related Links

  • JavaScript Tutorial
  • JavaScript Examples