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The ignoreCase property indicates whether or not the "i" flag is used with the regular expression. ignoreCase is a read-only property of an individual regular expression instance.

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


The value of ignoreCase is a Boolean and true if the "i" flag was used; otherwise, false. The "i" flag indicates that case should be ignored while attempting a match in a string.

You cannot change this property directly.


Using ignoreCase

var regex = new RegExp('foo', 'i');

console.log(regex.ignoreCase); // true


Specification Status Comment
ECMAScript 3rd Edition (ECMA-262) Standard Initial definition. Implemented in JavaScript 1.2. JavaScript 1.5: ignoreCase is a property of a RegExp instance, not the RegExp object.
ECMAScript 5.1 (ECMA-262)
The definition of 'RegExp.prototype.ignoreCase' in that specification.
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'RegExp.prototype.ignoreCase' in that specification.
Standard ignoreCase is now a prototype accessor property rather than an instance's own data property.
ECMAScript Latest Draft (ECMA-262)
The definition of 'RegExp.prototype.ignoreCase' in that specification.

Browser compatibility

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari
Basic support (Yes) (Yes) (Yes) (Yes) (Yes) (Yes)
Prototype accessor property ? ? 38 (38) ? ? ?
Feature Android Chrome for Android Edge Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support (Yes) (Yes) (Yes) (Yes) (Yes) (Yes) (Yes)
Prototype accessor property ? ? ? 38.0 (38) ? ? ?

See also

Document Tags and Contributors

 Contributors to this page: jameshkramer, fscholz, Mingun, Sheppy, Mgjbot, Maian, Prodoc, Dria
 Last updated by: jameshkramer,