How to pull a number out of a string in JavaScript and a regex?

Question

Using javascript -- I need to pull out and examine the number that appears just before the "jpg" file extension, in this case "300".

var filename = 2012_honda_odyssey_passenger-minivan_ex_s_oem_2_300.jpg

What's the best way to pull this number out -- I can alway assume it will be between the last "_" in the string and this final "." before the file extension.

I'm guessing that I need to do something with regex. Like this ....

var num = parseInt(filename.match(/some-regex-here/), 10);

addition

I did come up with this ... but it seemed very kludgy.

var filename = "2012_honda_odyssey_passenger-minivan_ex_s_oem_2_300.jpg";
var num = parseInt(filename.split('_').splice(-1,1).toString().split(".").splice(0,1).toString(), 10);

See me answer to [this question](http://stackoverflow.com/questions/12626898/jquery-regex-to-parse-image-name/12627019#12627019). It's pretty much the same thing. — Martin Ender, Sep 28 '12 at 05:35

score 1 · Answer 1 · answered Sep 28 '12 at 05:35

1

var filename = "2012_honda_odyssey_passenger-minivan_ex_s_oem_2_300.jpg";
var regex = /^.*_(\d+)\.jpg?$/;
var match = regex.exec(filename);
var number = Number(match[1]);

console.log(number);

answered Sep 28 '12 at 05:35

driangle

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score 0 · Answer 2 · edited May 23 '17 at 11:58

A regular expression such as this: _(\d+)\..+?$ should allow you to match and extract the number to a group. The regex above should match an underscore (_) followed by one ore more digits (\d+), followed by a period (\.) which in turn is followed by some letters (.+?) and finally the end of the string ($).

You can then refer to this previous SO question to see how you can later access these groups.

score 0 · Answer 3 · answered Sep 28 '12 at 05:35

0

var num=parseInt(filename.replace(/^.*?([0-9]+).jpg$/i,"$1"),10);

answered Sep 28 '12 at 05:35

Passerby

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score 0 · Answer 4 · answered Sep 28 '12 at 05:36

0

Avoiding regexes is usually best, unless you're doing complex string pattern matching is usually. Something like will get what you want:

var num = +filename.substring(
  filename.lastIndexOf('_') + 1,
  filename.lastIndexOf('.')
);

answered Sep 28 '12 at 05:36

Paul

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score 0 · Answer 5 · answered Sep 28 '12 at 05:39

0

try this:

'2012_honda_odyssey_passenger-minivan_ex_s_oem_2_300.jpg'.match(/[0-9]+(?=\.jpg)/)[0]

answered Sep 28 '12 at 05:39

turtledove

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score -1 · Accepted Answer · answered Sep 28 '12 at 05:37

-1

I feel a regex is overkill for something this simple, I would just use this:

var start = filename.lastIndexOf('_') + 1; 
var end = filename.lastIndexOf('.');
var num = parseInt(filename.substring(start, end), 10);

answered Sep 28 '12 at 05:37

verdesmarald

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I feel eventhough this is an acceptable answer to the situation where the OP is. It doesn't answer the real question "how to pull a number out of regex ? ". Can you please edit the answer to help people who came here actually looking for a way to parse the number from a string. @ggreiner 's answer seems closer. – Vasif Jul 28 '16 at 23:41

How to pull a number out of a string in JavaScript and a regex?

6 Answers6