The sticky property reflects whether or not the search is sticky (searches in strings only from the index indicated by the lastIndex property of this regular expression). sticky is a read-only property of an individual regular expression object.

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

Description

The value of sticky is a Boolean and true if the "y" flag was used; otherwise, false. The "y" flag indicates that it matches only from the index indicated by the lastIndex property of this regular expression in the target string (and does not attempt to match from any later indexes). A regular expression defined as both sticky and global ignores the global flag.

You cannot change this property directly. It is read-only.

Examples

Using a regular expression with the sticky flag

var str = '#foo#';
var regex = /foo/y;

regex.lastIndex = 1;
regex.test(str); // true
regex.lastIndex = 5;
regex.test(str); // false (lastIndex is taken into account with sticky flag)
regex.lastIndex; // 0 (reset after match failure)

Anchored sticky flag

For several versions, Firefox's SpiderMonkey engine had a bug with regard to the ^ assertion and the sticky flag which allowed expressions starting with the ^ assertion and using the sticky flag to match when they shouldn't. The bug was introduced some time after Firefox 3.6 (which had the sticky flag but not the bug) and fixed in 2015. Perhaps because of the bug, the ES2015 specification specifically calls out the fact that:

When the y flag is used with a pattern, ^ always matches only at the beginning of the input, or (if multiline is true) at the beginning of a line.

Examples of correct behavior:

var regex = /^foo/y;
regex.lastIndex = 2;
regex.test('..foo');   // false - index 2 is not the beginning of the string

var regex2 = /^foo/my;
regex2.lastIndex = 2;
regex2.test('..foo');  // false - index 2 is not the beginning of the string or line
regex2.lastIndex = 2;
regex2.test('.\nfoo'); // true - index 2 is the beginning of a line

Specifications

Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'RegExp.prototype.sticky' in that specification.
Standard Initial definition.
ECMAScript Latest Draft (ECMA-262)
The definition of 'RegExp.prototype.sticky' in that specification.
Draft  

Browser compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidEdge MobileFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
Basic supportChrome Full support 49Edge Full support 13Firefox Full support 3IE No support NoOpera Full support 36Safari Full support 10WebView Android Full support 49Chrome Android Full support 49Edge Mobile Full support YesFirefox Android Full support 4Opera Android Full support 36Safari iOS Full support 10Samsung Internet Android Full support 5.0nodejs Full support Yes
Prototype accessor property (ES2015)Chrome Full support YesEdge ? Firefox Full support 38IE ? Opera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesEdge Mobile ? Firefox Android Full support 38Opera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yesnodejs Full support Yes
Anchored sticky flag behavior per ES2015Chrome Full support YesEdge Full support YesFirefox Full support 44IE No support NoOpera Full support YesSafari Full support YesWebView Android ? Chrome Android Full support YesEdge Mobile Full support YesFirefox Android Full support 44Opera Android ? Safari iOS ? Samsung Internet Android Full support Yesnodejs ?

Legend

Full support  
Full support
No support  
No support
Compatibility unknown  
Compatibility unknown

See also

Document Tags and Contributors

Last updated by: wbamberg,