Web/JavaScript/Reference/Global objects/RegExp/sticky

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.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

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
ECMAScript (ECMA-262)The definition of 'RegExp.prototype.sticky' in that specification.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
`sticky`	Chrome Full support 49	Edge Full support 13	Firefox Full support 3	IE No support No	Opera Full support 36	Safari Full support 10	WebView Android Full support 49	Chrome Android Full support 49	Firefox Android Full support 4	Opera Android Full support 36	Safari iOS Full support 10	Samsung Internet Android Full support 5.0	nodejs Full support Yes
Anchored sticky flag behavior per ES2015	Chrome Full support 49	Edge Full support 13	Firefox Full support 44	IE No support No	Opera Full support 36	Safari Full support 10	WebView Android Full support 49	Chrome Android Full support 49	Firefox Android Full support 44	Opera Android Full support 36	Safari iOS Full support 10	Samsung Internet Android Full support 5.0	nodejs ?
Prototype accessor property (ES2015)	Chrome Full support 49	Edge Full support 13	Firefox Full support 38	IE No support No	Opera Full support 36	Safari Full support 10	WebView Android Full support 49	Chrome Android Full support 49	Firefox Android Full support 38	Opera Android Full support 36	Safari iOS Full support 10	Samsung Internet Android Full support 5.0	nodejs Full support Yes

Legend

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