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);

Answer 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.

Answer 2

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

Answer 3

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

Answer 4

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; });