returning part of regex string in javascript

Question

I want to get the video id of a youtube video using regex.

I have the following regex:

var VideoID = inputstring.match(/watch\?v=[A-Z,a-z,0-9]+($|\&)/);

This works fine. If i for instance put in:

https://www.youtube.com/watch?v=prHVlkFM9oc&index=9&list=RDxEwgEw3k6UA

It return this:

watch?v=prHVlkFM9oc&

But I only want the [A-Z,a-z,0-9]+ part of the regex (prHVlkFM9oc in the above code).

How do I get this? I could cut away 9 chars from the start after the regex returns, but that shouldn't be necessary.

Commas in a character class have no special meaning and are not used to separate ranges, so you can remove them. & is not a special character in a pattern, there is no need to escape it. — Casimir et Hippolyte
– Casimir et Hippolyte, Commented Feb 25, 2015 at 22:35
regular expressions are the wrong tool for parsing a query string. — zzzzBov
– zzzzBov, Commented Feb 25, 2015 at 22:41

Casimir et Hippolyte · Accepted Answer · 2015-02-25 23:37:02Z

1

Simply use parenthesis ( ) to catch the part that you want to grab:

var match = inputstring.match(/watch\?v=([A-Za-z0-9]+)($|&)/);

// returns ["watch?v=prHVlkFM9oc&", "prHVlkFM9oc", "&"]

Now your result is in match[1];

edited Feb 25, 2015 at 23:37

Casimir et Hippolyte

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answered Feb 25, 2015 at 22:33

floribon

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anubhava · Accepted Answer · 2015-02-25 22:33:31Z

1

You can use a captured group here and grab the first index of the resulting array:

var VideoID = ( inputstring.match(/watch\?v=([^&]+)/) || ['', ''])[1];
//=> prHVlkFM9oc

answered Feb 25, 2015 at 22:33

anubhava

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3 Comments

MyrionSC2 Over a year ago

I presume case [' ', ' '] fires if the first regex returns no matches?

anubhava Over a year ago

yes that is for safeguard measure if matches fail.

floribon Over a year ago

Good idea, deserves an upvote, however why not simply use [] instead of ['',''], the match would be undefined which makes total sense.

DoubleK · Accepted Answer · 2015-02-25 22:42:01Z

1

Well, if you are ok with VideoId variable you can do folowing: var parts = VideoId.split("="); so you can get that part as parts[1]

answered Feb 25, 2015 at 22:42

DoubleK

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