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    The source property returns a String containing the source text of the regexp object, and it doesn't contain the two forward slashes on both sides and any flags.

    Property attributes of RegExp.prototype.source
    Writable no
    Enumerable no
    Configurable yes


    Example: Using source

    var regex = /fooBar/ig;
    console.log(regex.source); // "fooBar", doesn't contain /.../ and "ig".

    Example: Empty regular expressions and escaping

    Starting with ECMAScript 5, the source property no longer returns an empty string for empty regular expressions. Instead, the string "(?:)" is returned. In addition, line terminators (such as "\n") are escaped now.

    new RegExp().source; // "(?:)"
    new RegExp('\n').source === "\n";  // true, prior to ES5
    new RegExp('\n').source === "\\n"; // true, starting with ES5


    Specification Status Comment
    ECMAScript 3rd Edition. Standard Initial definition. Implemented in JavaScript 1.2.
    JavaScript 1.5: source is a property of a RegExp instance, not the RegExp object.
    ECMAScript 5.1 (ECMA-262)
    The definition of 'RegExp.prototype.source' in that specification.
    Standard The source property for empty regular expressions now returns "(?:)" instead of an empty string. A definition for the escaping behavior has been added.
    ECMAScript 6 (ECMA-262)
    The definition of 'RegExp.prototype.source' in that specification.
    Release Candidate source is now a prototype accessor property rather than an instance's own data property.

    Browser compatibility

    Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
    Basic support (Yes) (Yes) (Yes) (Yes) (Yes)
    "(?:)" for empty regexps ? 38 (38) ? ? (Yes)
    Escaping ? 38 (38) ? ? ?
    Prototype accessor property ? 39 (39) [1] ? ? ?
    Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
    Basic support (Yes) (Yes) (Yes) (Yes) (Yes) (Yes)
    "(?:)" for empty regexps ? ? 38.0 (38) ? ? ?
    Escaping ? ? 38.0 (38) ? ? ?
    Prototype accessor property ? ? 39.0 (39) [1] ? ? ?

    Firefox-specific notes

    • [1] Prototype accessor property is backed out from Gecko 38 (Firefox 38 / Thunderbird 38 / SeaMonkey 2.35), due to web compatibility issue (bug 1150297).

    See also

    Document Tags and Contributors

    Contributors to this page: arai, Sheppy, fscholz, Mingun, ziyunfei, Prodoc, Mgjbot, Maian, Dria
    Last updated by: arai,