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.

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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

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

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


ECMAScript Language Specification
# sec-get-regexp.prototype.ignorecase

Browser compatibility

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See also