Web/JavaScript/Reference/Global objects/Symbol/for

The Symbol.for(key) method searches for existing symbols in a runtime-wide symbol registry with the given key and returns it if found. Otherwise a new symbol gets created in the global symbol registry with this key.

Syntax

Symbol.for(key);

Parameters

key: String, required. The key for the symbol (and also used for the description of the symbol).

Return value

An existing symbol with the given key if found; otherwise, a new symbol is created and returned.

Description

In contrast to Symbol(), the Symbol.for() function creates a symbol available in a global symbol registry list. Symbol.for() does also not necessarily create a new symbol on every call, but checks first if a symbol with the given key is already present in the registry. In that case, that symbol is returned. If no symbol with the given key is found, Symbol.for() will create a new global symbol.

Global symbol registry

The global symbol registry is a list with the following record structure and it is initialized empty:

A record in the global symbol registry
Field name	Value
Web/JavaScript/Reference/Global objects/Symbol/key	A string key used to identify a symbol.
Web/JavaScript/Reference/Global objects/Symbol/symbol	A symbol that is stored globally.

Examples

Using Symbol.for()

Symbol.for('foo'); // create a new global symbol
Symbol.for('foo'); // retrieve the already created symbol

// Same global symbol, but not locally
Symbol.for('bar') === Symbol.for('bar'); // true
Symbol('bar') === Symbol('bar'); // false

// The key is also used as the description
var sym = Symbol.for('mario');
sym.toString(); // "Symbol(mario)"

To avoid name clashes with your global symbol keys and other (library code) global symbols, it might be a good idea to prefix your symbols:

Symbol.for('mdn.foo');
Symbol.for('mdn.bar');

Specifications

Specification
ECMAScript (ECMA-262)The definition of 'Symbol.for' in that specification.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
`for`	Chrome Full support 40	Edge Full support 12	Firefox Full support 36	IE No support No	Opera Full support 27	Safari Full support 9	WebView Android Full support 40	Chrome Android Full support 40	Firefox Android Full support 36	Opera Android Full support 27	Safari iOS Full support 9	Samsung Internet Android Full support 4.0	nodejs Full support 0.12

Legend

Full support: Full support
No support: No support