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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).
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
This behavior was specified in ES2015 and differs from a previous Firefox implementation: "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".
var regex = /^foo/y; regex.lastIndex = 2; // disallows to match at the beginning of the string regex.test("..foo"); // false var regex2 = /^foo/my; regex2.lastIndex = 2; regex2.test("..foo"); // false regex2.lastIndex = 2; regex2.test(".\nfoo"); // true
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'RegExp.prototype.sticky' in that specification. |
Standard | Initial definition. |
ECMAScript 2017 Draft (ECMA-262) The definition of 'RegExp.prototype.sticky' in that specification. |
Draft |
Browser compatibility
Feature | Chrome | Edge | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|---|
Basic support | No support | (Yes) | 3.0 (1.9) | No support | No support | No support |
Prototype accessor property | No support | (Yes) | 38 (38) | No support | No support | No support |
Anchored sticky(y) flag behavior per ES2015 | No support | (Yes) | 44 (44) | No support | No support | No support |
Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|
Basic support | No support | No support | 1.0 (1.9) | No support | No support | No support |
Prototype accessor property | No support | No support | 38.0 (38) | No support | No support | No support |
Anchored sticky(y) flag behavior per ES2015 | No support | No support | 44.0 (44) | No support | No support | No support |