how to change uppercase to lowercase with regex javascript

Question

It could be any string, it should match only the UPPERCASE part and change to lowercase, for example:

"It's around August AND THEN I get an email"

become

"It's around August and then I get an email"

as you can see the word It's, August and I should be ignored

Do you have any parameters that define what should be ignored/not ignored? — Alex W
– Alex W, Commented Aug 27, 2015 at 18:31
Why should It's August I be ignored? Is there any hidden requirements there? Like, the first word of the sentence should be preserved, the month names,.... — Alfonso Presa
– Alfonso Presa, Commented Aug 27, 2015 at 18:31
Why use RegEx for this? its as simple as value.toLowerCase() — maraaaaaaaa
– maraaaaaaaa, Commented Aug 27, 2015 at 18:37

mplungjan · Accepted Answer · 2019-08-22 11:20:54Z

34

Use /\b[A-Z]{2,}\b/g to match all-caps words and then .replace() with a callback that lowercases matches.

var string = "It's around August AND THEN I get an email",
  regex = /\b[A-Z]{2,}\b/g;

var modified = string.replace(regex, function(match) {
  return match.toLowerCase();
});

console.log(modified);
// It's around August and then I get an email

Also, feel free to use a more complicated expression. This one will look for capitalized words with 1+ length with "I" as the exception (I also made one that looked at the first word of a sentence different, but that was more complicated and requires updated logic in the callback function since you still want the first letter capitalized):

\b(?!I\b)[A-Z]+\b

edited Aug 22, 2019 at 11:20

mplungjan

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answered Aug 27, 2015 at 18:32

Sam

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1 Comment

jbuddy Over a year ago

Any chance the replacement from upper-case to lower-case can be done by the regex engine itself?

baao · Accepted Answer · 2015-08-27 18:32:42Z

5

A solution without regex:

function isUpperCase(str) {
        return str === str.toUpperCase();
    }

var str = "It's around August AND THEN I get an email";
var matched = str.split(' ').map(function(val){
  if (isUpperCase(val) && val.length>1) {
    return val.toLowerCase();
    }
  return val;        
});

console.log(matched.join(' '));

answered Aug 27, 2015 at 18:32

baao

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1 Comment

John Smith Over a year ago

Cool, this solution is useful for another problem I had, thanks!

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