The JavaScript exception "variable is a reserved identifier" occurswhenreserved keywords are used as identifiers.

Message

SyntaxError: Unexpected reserved word (V8-based)SyntaxError: implements is a reserved identifier (Firefox)SyntaxError: Cannot use the reserved word 'implements' as a variable name. (Safari)

Error type

What went wrong?

Reserved keywords will throw inif they are used as identifiers. These are reserved instrict mode and sloppy mode:

• enum

The following are only reserved when they are found in strict mode code:

• implements
• interface
• let
• package
• private
• protected
• public
• static

Examples

Strict and non-strict reserved keywords

Theenum identifier is generally reserved.

const enum = { RED: 0, GREEN: 1, BLUE: 2 };// SyntaxError: enum is a reserved identifier

In strict mode code, more identifiers are reserved.

"use strict";const package = ["potatoes", "rice", "fries"];// SyntaxError: package is a reserved identifier

You'll need to rename these variables.

const colorEnum = { RED: 0, GREEN: 1, BLUE: 2 };const list = ["potatoes", "rice", "fries"];

Update older browsers

If you are using an older browser that does not yet implementlet orclass,for example, you should update to a more recent browser version that does support thesenew language features.

"use strict";class DocArchiver {}// SyntaxError: class is a reserved identifier// (throws in older browsers only, e.g. Firefox 44 and older)

See also

• Lexical grammar