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    function

    Summary

    The function keyword can be used to define a function inside an expression.

    Syntax

    function [name]([param1[, param2[, ..., paramN]]]) {
       statements
    }

    Parameters

    name
    The function name. Can be omitted, in which case the function is anonymous. The name is only local to the function body.
    paramN
    The name of an argument to be passed to the function. A function can have up to 255 arguments.
    statements
    The statements which comprise the body of the function.

    Description

    A function expression is very similar to and has almost the same syntax as a function statement (see function statement for details). The main difference between a function expression and a function statement is the function name, which can be omitted in function expressions to create anonymous functions. See also the chapter about functions for more information.

    Examples

    The following example defines an unnamed function and assigns it to x. The function returns the square of its argument:

    var x = function(y) {
       return y * y;
    };
    

    Named function expression

    If you want to refer to the current function inside the function body, you need to create a named function expression. This name is then local only to the function body (scope). This also avoids using the non-standard arguments.callee property.

    var math = {
      'factorial': function factorial(n) {
        if (n <= 1)
          return 1;
        return n * factorial(n - 1);
      }
    };
    

    Specifications

    Specification Status Comment
    ECMAScript 3rd Edition. Standard Initial definition. Implemented in JavaScript 1.5
    ECMAScript 5.1 (ECMA-262)
    The definition of 'Function definition' in that specification.
    Standard  
    ECMAScript 6 (ECMA-262)
    The definition of 'Function definitions' in that specification.
    Draft  

    Browser compatibility

    Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
    Basic support (Yes) (Yes) (Yes) (Yes) (Yes)
    Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
    Basic support (Yes) (Yes) (Yes) (Yes) (Yes) (Yes)

    See also

    Document Tags and Contributors

    Contributors to this page: Sevenspade
    Last updated by: Sevenspade,
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