Regex to capture whole word with specific beginning

Question

I need to capture a number passed as appended integers to a CSS class. My regex is pretty weak, what I'm looking to do is pretty simple. I thought that "negative word boundary" \B was the flag I wanted but I guess I was wrong

string = "foo bar-15";
var theInteger = string.replace('/bar\-\B', ''); // expected result = 15

score 3 · Accepted Answer · edited May 23 '17 at 10:34

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Use a capture group as outlined here:

var str= "foo bar-15";
var regex = /bar-(\d+)/;
var theInteger = str.match(regex) ? str.match(regex)[1] : null;

Then you can just do an if (theInteger) wherever you need to use it

edited May 23 '17 at 10:34

Community

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answered Oct 24 '12 at 00:26

JamesSwift

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The problem here is that if there are no trailing digits, `match` returns `null` and attempting to access `null[1]` will throw an error. Better to first call `match`, then check the result before going further (see my answer). – RobG Oct 24 '12 at 02:17
Even prettier is `theInteger = str.match(regex) ? RegExp.$1 : null` – Sean Kinsey Oct 24 '12 at 02:24
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@SeanKinsey—let's get silly. If `null` is an OK result, then `theInteger = str.match(regex) && RegExp.$1;` is prettiest (so far). – RobG Oct 24 '12 at 03:37
@RobG, sure I just hate misusing the && operator as a conditional operator. – Sean Kinsey Oct 24 '12 at 03:49
Hey, Crockford says it's OK as the ["guard"](http://www.crockford.com/javascript/survey.html), so that gives me *carte blance*, doesn't it? ;-) – RobG Oct 24 '12 at 05:10
Thanks for thinking it through so much @JamesSwift - looks great :) – Brian Oct 24 '12 at 16:01

score 1 · Answer 2 · answered Oct 24 '12 at 00:21

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Try this:

var theInteger = string.match(/\d+/g).join('')

answered Oct 24 '12 at 00:21

Ram

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Nah - I want to be future-proof against other integer-based classes being introduced into the CSS. Matching the "bar-" characters and removing them to get the integer is necessary. – Brian Oct 24 '12 at 00:23

score 1 · Answer 3 · answered Oct 24 '12 at 00:25

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string = "foo bar-15";
var theInteger = /bar-(\d+)/.exec(string)[1]
theInteger // = 15

answered Oct 24 '12 at 00:25

Sean Kinsey

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score 1 · Answer 4 · answered Oct 24 '12 at 02:14

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If you just want the digits at the end (a kind of reverse parseInt), why not:

var num = 'foo bar-15'.replace(/.*\D+(\d+)$/,'$1');

or

var m = 'foo bar-15'.match(/\d+$/);
var num = m? m[0] : '';

answered Oct 24 '12 at 02:14

RobG

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Regex to capture whole word with specific beginning

4 Answers4