Why is this Regex not working for JavaScript?

Question

The code is suppose to say matched! for the given string. I tried multiple things and cannot get it to work.

HTML:

<div id="ssn">123-45-6789</div>

js:

var regex = new RegExp("^\d{3}-\d{2}-\d{4}$");

$("#div")
    .filter(function() {
        return this.innerHTML.match(regex);
    })
    .html("Matched!")
;

Your <div> has the id "ssn", but your jQuery selector says "#div" ... — Pointy
– Pointy, Commented Jan 15, 2015 at 23:25

Pointy · Accepted Answer · 2015-01-15 23:17:12Z

4

Use native regular expression syntax when you can:

var regex = /^\d{3}-\d{2}-\d{4}$/;

When you construct a regular expression from a string, you have to double-up on the \ characters because it's a metacharacter in string constant token syntax too. If you don't, then by the time JavaScript passes the regular expression string to the RegExp constructor, the backslashes are gone.

You'd probably be better off using .test() in your filter function:

$("#div")
    .filter(function() {
        return regex.test(this.innerHTML);
    })
    .html("Matched!")
;

answered Jan 15, 2015 at 23:17

Pointy

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4 Comments

Diego Over a year ago

Another point would be that $("#div") should actually be $("#ssn") as there is no element with id div in the example.

Pointy Over a year ago

@Diego yes; I assumed that was just a transcription error.

photonacl Over a year ago

wow thanks Pointy, worked like a charm! May I know what is the difference for .test() vs .match() ? Thanks.

Pointy Over a year ago

@photonacl .test() just returns a boolean ("did it match or not?").

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