RegEx - Get All Characters After Last Slash in URL

Question

I'm working with a Google API that returns IDs in the below format, which I've saved as a string. How can I write a Regular Expression in javascript to trim the string to only the characters after the last slash in the URL.

var id = 'http://www.google.com/m8/feeds/contacts/myemail%40gmail.com/base/nabb80191e23b7d9'

lonesomeday · Answer 1 · 2023-07-31T20:26:04.857

108

Don't write a regex! This is trivial to do with string functions instead:

var final = id.substring(id.lastIndexOf('/') + 1);

It's even easier if you know that the final part will always be 16 characters:

var final = id.substring(id.length - 16);

edited Jul 31 '23 at 20:26

answered Nov 04 '13 at 21:00

lonesomeday

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Will not return anything is the url is `'http://www.google.com/m8/feeds/contacts/myemail%40gmail.com/base/nabb80191e23b7d9/'` – Allan Kimmer Jensen Mar 17 '15 at 15:48
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@AllanKimmerJensen Well, there isn't anything after the last slash there, of course. – lonesomeday Mar 17 '15 at 22:58
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I found this topic although I was looking for a PHP solution. I converted it, in case anyone is interested: `substr($id, strrpos($id, "/") + 1)` – Jan Sep 30 '15 at 14:12
Not an answer to the question! – LinusGeffarth Oct 27 '20 at 10:46
@LinusGeffarth https://meta.stackexchange.com/questions/66377/what-is-the-xy-problem – lonesomeday Oct 27 '20 at 13:24
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Why is this so upvoted? This shows up as the first question on google when searching for a regex solution. OP specifically asked for a regex, and the answer starts with "Don't write a regex" : ( – Mercury Feb 14 '22 at 11:51
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@Mercury Cos it's sensible advice? "How do I knock a nail into a wall with a harpsichord?" "Don't: use a hammer." – lonesomeday Feb 14 '22 at 18:05
substr is deprecated – Dinesh Jun 08 '23 at 00:59
@Dinesh It won't make a difference here and it'll never be removed from browsers, but yes, it is, and I've updated the code as you say. – lonesomeday Jul 31 '23 at 20:25

jfriend00 · Answer 2 · 2016-02-22T07:25:55.877

55

A slightly different regex approach:

var afterSlashChars = id.match(/\/([^\/]+)\/?$/)[1];

Breaking down this regex:

\/ match a slash
(  start of a captured group within the match
[^\/] match a non-slash character
+ match one of more of the non-slash characters
)  end of the captured group
\/? allow one optional / at the end of the string
$  match to the end of the string

The [1] then retrieves the first captured group within the match

Working snippet:

var id = 'http://www.google.com/m8/feeds/contacts/myemail%40gmail.com/base/nabb80191e23b7d9';

var afterSlashChars = id.match(/\/([^\/]+)\/?$/)[1];

// display result
document.write(afterSlashChars);

edited Feb 22 '16 at 07:25

answered Nov 04 '13 at 21:02

jfriend00

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Explanations make your answer much more valuable, than accepted one. Thanks! – Ilia Ross Sep 24 '14 at 11:56
@IliaRostovtsev: Unfortunately, the explanation is wrong, and so is the answer. Non-greedy quantifiers don't guarantee the shortest possible match, because they only affect where the match *ends*, not where it begins. This regex matches from the *first* slash to the end. – Alan Moore Feb 22 '16 at 07:17
@Alan Moore I don't know why I picked this answer, probably because it fitted me at the moment. Thank you for your explanation. – Ilia Ross Feb 22 '16 at 07:20
@AlanMoore - I modified the answer and added a working snippet. – jfriend00 Feb 22 '16 at 07:21
@IliaRostovtsev - I modified the answer and added a working snippet. – jfriend00 Feb 22 '16 at 07:23
Okay, now it *is* the best answer. :D – Alan Moore Feb 22 '16 at 07:41
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@jfriend00 great answer and awesome explanation around your RegEx! – Paul Jul 22 '16 at 16:11

score 31 · Answer 3 · answered Jan 20 '15 at 21:12

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Just in case someone else comes across this thread and is looking for a simple JS solution:

id.split('/').pop(-1)

answered Jan 20 '15 at 21:12

ramumb

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Easy, short and nice. But the -1 argument seems redundant, as pop() always returns the last element. – JHH Jun 10 '15 at 09:04
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This is genius! And elegant – ecairol Nov 08 '18 at 20:01
Regexp seems to be faster https://jsperf.com/last-element-of-array-xxx/2 – koral Nov 29 '18 at 12:35

score 28 · Answer 4 · answered Feb 22 '16 at 06:56

this is easy to understand (?!.*/).+

let me explain:

first, lets match everything that has a slash at the end, ok? that's the part we don't want

.*/ matches everything until the last slash

then, we make a "Negative lookahead" (?!) to say "I don't want this, discard it"

(?!.*) this is "Negative lookahead"

Now we can happily take whatever is next to what we don't want with this .+

YOU MAY NEED TO ESCAPE THE / SO IT BECOMES:

(?!.*\/).+

score 13 · Answer 5 · edited Jan 22 '18 at 17:17

13

this regexp: [^\/]+$ - works like a champ:

var id = ".../base/nabb80191e23b7d9"

result = id.match(/[^\/]+$/)[0];

// results -> "nabb80191e23b7d9"

edited Jan 22 '18 at 17:17

Kamil Kiełczewski

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answered Dec 22 '17 at 22:26

Andy

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score 9 · Answer 6 · answered Nov 04 '13 at 20:59

9

This should work:

last = id.match(/\/([^/]*)$/)[1];
//=> nabb80191e23b7d9

answered Nov 04 '13 at 20:59

anubhava

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Good answer. In Perl, regex delimeters must be escaped, even in character classes, otherwise it wouldn't find the regex to be parsed. – Nov 04 '13 at 21:25

score 7 · Answer 7 · answered Nov 04 '13 at 21:20

7

Don't know JS, using others examples (and a guess) -

id = id.match(/[^\/]*$/); // [0] optional ?

answered Nov 04 '13 at 21:20

Just for the record, the match function returns an array.Using [0] is going to return just the first one. It's not optional. – brduca Sep 11 '14 at 17:07
There are no capture groups in this regex, isn't match overloaded to return the whole match if no index is referenced? – Sep 30 '14 at 23:27

score 4 · Answer 8 · answered Feb 07 '19 at 12:16

4

Why not use replace?

"http://google.com/aaa".replace(/(.*\/)*/,"")

yields "aaa"

answered Feb 07 '19 at 12:16

Nimrod

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RegEx - Get All Characters After Last Slash in URL

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