Javascript regex return capture group value

Question

I am parsing a youtube URL and I want to get the video id but I'm having such a hard time

The only way I could come up with is this

href = 'https://www.youtube.com/watch?v=-UI86rRSHkg'

...

video = href.replace(/^.*?youtube\.com\/.*?v=(.+?)(?:&|$).*/i, '$1');

But I think there must be a better way to do this.

How can I get the value of a capture group in JavaScript regex?

developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…? — Bergi
– Bergi, Commented Sep 18, 2014 at 11:35
To the best of my knowledge the ? in ^.*?youtube is useless because the * means zero or more times, and the ? means it's optional, which is redundant. — Nateowami
– Nateowami, Commented Sep 18, 2014 at 11:37
@Nateowami ? after * or + means to not be greedy, to stop at the following-up pattern. So in my case URLs like youtube.com... ( missing schema and www ) would be valid. — php_nub_qq
– php_nub_qq, Commented Sep 18, 2014 at 11:43
OK, good point. But without the ? it would still match cases without scheme or www. — Nateowami
– Nateowami, Commented Sep 18, 2014 at 11:53
This question is using a youtube URL as an example but this questions is more generic i.e. Javascript regex return capture group value — anubhava
– anubhava, Commented Apr 30, 2021 at 6:24

anubhava · Accepted Answer · 2014-09-18 11:33:12Z

5

To get the matched info use String#match:

var id = href.match(/\byoutube\.com\/[^?]*\?v=([^&]+)/i)[1];

And to make it even safer use:

var id = (href.match(/\byoutube\.com\/[^?]*\?v=([^&]+)/i) || [null, null])[1];

2nd approach is for the case when ?v= is missing in href variable.

answered Sep 18, 2014 at 11:33

anubhava

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1 Comment

@Nateowami If the string doesn't match you'll get null back instead of an error.