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.
input property is a static property of regular expressions that contains the string against which a regular expression is matched.
RegExp.$_ is an alias for this property.
input property is static, it is not a property of an individual regular expression object. Instead, you always use it as
The value of the
input property is modified whenever the searched string on the regular expression is changed and that string is matching.
var re = /hi/g; re.test('hi there!'); RegExp.input; // "hi there!" re.test('foo'); // new test, non-matching RegExp.$_; // "hi there!" re.test('hi world!'); // new test, matching RegExp.$_; // "hi world!"
Non-standard. Not part of any current specification.