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regExp.source

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

Examples

Using source

var regex = /fooBar/ig;

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

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

Specifications

Specification Status Comment
ECMAScript 3rd Edition (ECMA-262) 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 2015 (6th Edition, ECMA-262)
The definition of 'RegExp.prototype.source' in that specification.
Standard source is now a prototype accessor property rather than an instance's own data property.
ECMAScript Latest Draft (ECMA-262)
The definition of 'RegExp.prototype.source' in that specification.
Draft

Browser compatibilityUpdate compatibility data on GitHub

Desktop
Chrome Edge Firefox Internet Explorer Opera Safari
Basic support Yes Yes 1 Yes Yes Yes
Prototype accessor property (ES2015) Yes ? 41 ? Yes Yes
Escaping ? ? 38 ? ? ?
"(?:)" for empty regexps Yes ? 38 ? ? Yes
Mobile
Android webview Chrome for Android Edge Mobile Firefox for Android Opera for Android iOS Safari Samsung Internet
Basic support Yes Yes Yes 4 Yes Yes Yes
Prototype accessor property (ES2015) Yes Yes ? 41 Yes Yes Yes
Escaping ? ? ? 38 ? ? ?
"(?:)" for empty regexps ? ? ? 38 ? ? ?
Server
Node.js
Basic support Yes
Prototype accessor property (ES2015) Yes
Escaping ?
"(?:)" for empty regexps ?

See also

© 2005–2018 Mozilla Developer Network and individual contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/source