Javascript regex match going in infinite loop

Question

this is the code I am trying :

var arr = [];
var str = "hey check this video out! youtube.com/watch?v=123456 and there is some other text youtube.com/watch?v=3t_3456 and some more.";
while (match = /youtube\.com\/watch\?v=([^\s]+)/.exec(str)) {
  arr.push(match[1]);
}
console.log(arr);

it should capture the last part of the url's and push them to an array.

the array I am expecting is :

["123456", "3t_3456"]

but this code is going in an infinite loop, what's wrong with it ?

You have a while loop performing the same action over and over with nothing changing its condition. You need to modify str or it will just keep checking the same string over and over. — JLRishe
– JLRishe, Commented May 21, 2014 at 6:15
but I took the code from stackoverflow.com/questions/432493/… — aelor
– aelor, Commented May 21, 2014 at 6:17

JLRishe · Accepted Answer · 2017-09-27 13:10:35Z

7

The difference between your code and the page you linked to is:

You are creating a new regex on every iteration of the loop, so it is not maintaining a record of the previous matches.
You are not using the g (global) flag, so even if you were not creating new regexes, it would just keep finding the first match.

You need to reuse the same regex, and use the g flag:

var pattern = /youtube\.com\/watch\?v=([^\s]+)/g;
while (match = pattern.exec(str)) {
    arr.push(match[1]);
}

edited Sep 27, 2017 at 13:10

answered May 21, 2014 at 6:19

JLRishe

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1 Comment

Abs Over a year ago

Have a look here stackoverflow.com/a/33016026/380733 sometimes you need an extra condition as explained there

JLRishe · Accepted Answer · 2014-05-21 06:33:21Z

2

You are inviting an infinite loop without using the global flag in your regex.

var arr = [];
var str = "hey check this video out! youtube.com/watch?v=123456 and there is some other text youtube.com/watch?v=3t_3456 and some more.";
var re = /youtube\.com\/watch\?v=([^\s]+)/g;
while (match = re.exec(str)) {
  arr.push(match[1]);
}
console.log(arr);

See a working example here.

Without the g flag you'd run into an infinite loop, see here (WARNING: Clicking this link may crash your browser.).

edited May 21, 2014 at 6:33

JLRishe

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answered May 21, 2014 at 6:19

devnull

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