Increment a number in a string in with regex

Question

I get the name of an input element, which is a string with a number (url1). I want to increment the number by 1 (url2) in the easiest and quickest way possible.

My way would be to get \d / restofstring, ++ the match, then put together number with restofstring. Is there a better way?

Update:

My final (dummy)code became:

var liNew = document.createElement('li'); 
liNew.innerHTML = liOld.innerHTML; 
var els = Y.Dom.getChildrenBy(liNew, function(el) { 
    return el.name.match(/\d+$/); 
} // YUI method where the function is a test 
for (var i = 0, el; el = els[i]; i++) { 
    el.name = el.name.replace(/\d+$/, function(n) { return ++n }); 
} 
list.appendChild(liNew);

Er, you can't just change form element names like that in IE. You're gonna run into issues: http://stackoverflow.com/questions/1650797/setting-name-of-dom-created-element-fails-in-ie-workaround — Roatin Marth, Nov 16 '09 at 16:13
Ok, thanks for the heads up. If I end up needing to support IE for this, I'll use YUI Element instead. — Jacob Rask, Nov 16 '09 at 16:33

score 44 · Accepted Answer · answered Nov 16 '09 at 15:20

44

How about:

'url1'.replace(/\d+$/, function(n){ return ++n }); // "url2"
'url54'.replace(/\d+$/, function(n){ return ++n }); // "url55"

There we search for a number at the end of the string, cast it to Number, increment it by 1, and place it back in the string. I think that's the same algo you worded in your question even.

Reference:

String.prototype.replace - can take a regex

answered Nov 16 '09 at 15:20

Roatin Marth

23,589
3
51
55

Thanks, I updated the question with the solution I made with your example – Jacob Rask Nov 16 '09 at 15:55
2

This is a beautiful solution. – EricP May 28 '13 at 02:56
2

Here is a slightly modified version that works for all the numbers in a string: `"url5part6".replace(/\d+/g, function(n){ return ++n }); //returns "url6part7"` – starbeamrainbowlabs Nov 27 '14 at 09:23
Good answer but I fail to see the part where we "cast it to Number" – Spikolynn Aug 19 '16 at 14:57
`++` did that. It converts the operand to number implicitly and then increase that by one before returning the final value. – InSync Apr 25 '23 at 15:36

intgr · Answer 2 · 2009-11-16T15:32:44.597

7

Simple. Use a substitution function with regular expressions:

s = 'abc99abc';
s = s.replace(/\d+/, function(val) { return parseInt(val)+1; });

will set variable s to: abc100abc

But it gets more complicated if you want to make sure you only change a certain parameter in the URL:

s = '?foo=10&bar=99';
s = s.replace(/[&?]bar=\d+/, function(attr) {
  return attr.replace(/\d+/, function(val) { return parseInt(val)+1; });
});

will set variable s to: ?foo=10&bar=100

edited Nov 16 '09 at 15:32

answered Nov 16 '09 at 15:19

intgr

19,834
5
59
69

1

Hm, the question was not about get parameters? – Jacob Rask Nov 16 '09 at 15:39
If you read the question carefully, the asker did not specify what exactly he wanted to change; not even that the number would be *at the end* of the URL -- he just used it in his example. I figured changing GET parameters would be a likely use case. – intgr Nov 16 '09 at 16:33
"the name of an input element" = `` – Jacob Rask Nov 16 '09 at 16:44

score 2 · Answer 3 · answered Nov 16 '09 at 15:20

2

You can use replace and pass it a function to use to replace the matched section:

str.replace(/\d+/, function(number) { return parseInt(number, 10) + 1; });

answered Nov 16 '09 at 15:20

Phil Ross

25,590
9
67
77

score 1 · Answer 4 · answered Nov 16 '09 at 15:16

1

Looks OK. You might want to use a regex like ^(.*?)(\d+)$, making sure the number you're grabbing is at the end of the string.

answered Nov 16 '09 at 15:16

Tim Pietzcker

328,213
58
503
561

Increment a number in a string in with regex

4 Answers4

Linked

Related