up vote 1 down vote favorite

This deals with the general problem of extracting a signed number from a string that also contains hyphens.

Can someone please come up with the regex for the following:

 "item205"             => 205  
 "item-25              => -25  
 "item-name-25"        => -25

Basically, we want to extract the number to the end of the string, including the sign, while ignoring hyphens elsewhere.

The following works for the first two but returns "-name-25" for the last: 

var sampleString = "item-name-25";
sampleString.replace(/^(\d*)[^\-^0-9]*/, "")

Thanks!

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Any particular reason this was voted down? Seems perfectly valid... – Randy Hall Dec 7 '12 at 17:40
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2 Answers

up vote 4 down vote accepted

You can use .match instead:

"item-12-34".match(/-?\d+$/);  // ["-34"]

The regexp says "possible hyphen, then one or more digits, then the end of the string".

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up vote 4 down vote

Don't use replace. Instead, use match and write the regex for what you actually want (because that's a lot easier):

var regex = /-?\d+$/;
var match = "item-name-25".match(regex);
> ["-25"]
var number = match[0];

One thing about your regex though: in a character class you can only meaningfully use ^ once (right at the beginning) to mark it as a negated character class. It doesn't work for every single element individually. That means that your character class actually corresponds to "any character that is not a -, ^ or a digit.

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Was just about to post this. Hah. – Shmiddty Dec 7 '12 at 17:42
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