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    Symbol.for()

    This is a new technology, part of the ECMAScript 2015 (ES6) standard .
    This technology's specification has been finalized, but check the compatibility table for usage and implementation status in various browsers.

    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).

    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
    [[key]] A string key used to identify a symbol.
    [[symbol]] A symbol that is stored globally.

    Examples

    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 Status Comment
    ECMAScript 2015 (6th Edition, ECMA-262)
    The definition of 'Symbol.for' in that specification.
    Standard Initial definition.

    Browser compatibility

    Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
    Basic support 40 36.0 (36.0) Not supported Not supported Not supported
    Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
    Basic support Not supported Not supported 36.0 (36.0) Not supported Not supported Not supported

    See also

    Document Tags and Contributors

    Contributors to this page: fscholz, steelbrain
    Last updated by: fscholz,