RegExp.input ($_)

Non-standard: This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

The non-standard input property is a static property of regular expressions that contains the string against which a regular expression is matched. RegExp.$_ is an alias for this property.


The input property is static, it is not a property of an individual regular expression object. Instead, you always use it as RegExp.input or RegExp.$_.

The value of the input property is modified whenever the searched string on the regular expression is changed and that string is matching.


Using input and $_

const re = /hi/g;
re.test("hi there!");
RegExp.input; // "hi there!"
re.test("foo"); // new test, non-matching
RegExp.$_; // "hi there!"
re.test("hi world!"); // new test, matching
RegExp.$_; // "hi world!"


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Browser compatibility

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See also