Is there an easy way to change the case of a matched string with javascript?

Example

String : <li>something</li>

Regex : /<([\w]+)[^>]*>.*?<\/\1>/

And what I'd like to do is replace the match $1 to all capital letters (inside the replace if possible). I'm not entirely sure when $1 is a valid match and not a string -- '$1'.toUpperCase doesn't work.

So how would I go about returning <LI>something</li>? The method, not the regex.

Is there an easy way to change the case of a matched string with javascript?

Example

String : <li>something</li>

Regex : /<([\w]+)[^>]*>.*?<\/\1>/

And what I'd like to do is replace the match $1 to all capital letters (inside the replace if possible). I'm not entirely sure when $1 is a valid match and not a string -- '$1'.toUpperCase doesn't work.

So how would I go about returning <LI>something</li>? The method, not the regex.

• javascript
• regex

2 Answers 2

You can pass the replace method a replacer function. The first argument for which is the whole match, the second will be $1. Thus:

mystring.replace(/<([\w]+)[^>]*>.*?<\/\1>/, function(a,x){ 
   return a.replace(x,x.toUpperCase()); 
})

although this form saves the extra operation by making an additional capture (should be faster but haven't checked):

mystring.replace(/<([\w]+)([^>]*>.*?<\/\1>)/, function(a,x,y){ 
   return ('<'+x.toUpperCase()+y); 
})

easiest is probably to use a regex match and then use .toUpperCase on the match. I modified the regex slightly to add in a second capture group

var str = '<li>something</li>';
var arr = /<([\w]+)([^>]*>.*?<\/)\1>/.exec(str);
str = '<' + arr[1].toUpperCase() + arr[2] + arr[1].toUpperCase() + '>';