RegExp.prototype.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 compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
sourceChrome Full support 1Edge Full support 12Firefox Full support 1IE Full support 4Opera Full support YesSafari Full support YesWebView Android Full support 1Chrome Android Full support 18Firefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support 1.0nodejs Full support Yes
"(?:)" for empty regexpsChrome Full support 73Edge Full support 12Firefox Full support 38IE No support NoOpera Full support 60Safari Full support YesWebView Android Full support 73Chrome Android Full support 73Firefox Android Full support 38Opera Android Full support 52Safari iOS ? Samsung Internet Android No support Nonodejs ?
EscapingChrome Full support 73Edge Full support 12Firefox Full support 38IE Full support 10Opera Full support 60Safari ? WebView Android Full support 73Chrome Android Full support 73Firefox Android Full support 38Opera Android Full support 52Safari iOS ? Samsung Internet Android No support Nonodejs ?
Prototype accessor property (ES2015)Chrome Full support 48Edge Full support 12Firefox Full support 41IE Full support 4Opera Full support 35Safari Full support YesWebView Android Full support 48Chrome Android Full support 48Firefox Android Full support 41Opera Android Full support 35Safari iOS Full support YesSamsung Internet Android Full support 5.0nodejs Full support Yes

Legend

Full support  
Full support
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Compatibility unknown  
Compatibility unknown

See also