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 AndroidEdge MobileFirefox for AndroidOpera for AndroidiOS SafariSamsung InternetNode.js
Basic supportChrome Full support YesEdge Full support YesFirefox Full support 1IE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 4Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
Prototype accessor property (ES2015)Chrome Full support YesEdge ? Firefox Full support 41IE ? Opera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile ? Firefox Android Full support 41Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
EscapingChrome ? Edge ? Firefox Full support 38IE ? Opera ? Safari ? WebView Android ? Chrome Android ? Edge Mobile ? Firefox Android Full support 38Opera Android ? Safari iOS ? Samsung Internet Android ? nodejs ?
"(?:)" for empty regexpsChrome Full support YesEdge ? Firefox Full support 38IE ? Opera ? Safari Full support YesWebView Android ? Chrome Android ? Edge Mobile ? Firefox Android Full support 38Opera Android ? Safari iOS ? Samsung Internet Android ? nodejs ?

Legend

Full support  
Full support
Compatibility unknown  
Compatibility unknown

See also

Document Tags and Contributors

Last updated by: wbamberg,