Extract substring by regex

Question

I'm trying to extract a resource id using regex into a variable.

So far I managed to match the string, but I'm confused as to how to extract the digits into a separate value.

"/posts/23/edit".match(/\/posts\/(\d*)\/edit/g)
// => ["/posts/23/edit"]

Removing the /g gives you the digits in the second element in the resulting array. Any particular reason you put it there? — Biffen
– Biffen, Commented Aug 28, 2016 at 18:37

Tomalak · Accepted Answer · 2016-08-28 18:37:28Z

2

/\/posts\/(\d*)\/edit/g.exec("/posts/23/edit")
// => ["/posts/23/edit", "23"]

answered Aug 28, 2016 at 18:37

Tomalak

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8 Comments

Biffen Over a year ago

The answer itself could use an explanation…

ppeterka Over a year ago

(I didn't do any downvotes, but a bit of an explanation wouldn't hurt to teach the guy why not only how)

Tomalak Over a year ago

@Biffen Actually, I expect the OP do do some reading on their own. Really. This is a basic problem. The terseness of the answer testifies this. Flipping through the docs of RegExp#exec is actually necessary if you didn't know it before. Why would I have to write an excerpt of the documentation?

Tomalak Over a year ago

@ave I figured you are just missing a basic hint here and would be fine on your own after that.

Biffen Over a year ago

@Tomalak It's not that self-explanatory, IMHO. And it deserves a downvote partly for what ppeterka mentioned, and partly because ‘code dump’ answers make it seem like it's OK to use SO as a code-writing service. (Again; IMHO (which is what dictates my voting).)

|

Oriol · Accepted Answer · 2016-08-28 19:09:41Z

2

That's because you use the g (global) flag, which makes match ignore capturing groups.

If you are only interested in the first match, just remove the flag.

console.log("/posts/23/edit".match(/\/posts\/(\d*)\/edit/));
// [ "/posts/23/edit", "23" ]

Otherwise you should keep the flag and repeatedly call exec inside a loop.

var match, rg = /posts\/(\d*)\/edit/g;
while(match = rg.exec("/posts/23/edit -- /posts/24/edit")) {
  console.log(match);
}

edited Aug 28, 2016 at 19:09

answered Aug 28, 2016 at 19:01

Oriol

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