javascript - How to convert "camelCase" to "Camel Case"? - Stack Overflow

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I’ve been trying to get a JavaScript regex command to turn something like "thisString" into "This String" but the closest I’ve gotten is replacing a letter, resulting in something like "Thi String" or "This tring". Any ideas?

To clarify I can handle the simplicity of capitalizing a letter, I’m just not as strong with RegEx, and splitting "somethingLikeThis" into "something Like This" is where I’m having trouble.

I’ve been trying to get a JavaScript regex command to turn something like "thisString" into "This String" but the closest I’ve gotten is replacing a letter, resulting in something like "Thi String" or "This tring". Any ideas?

To clarify I can handle the simplicity of capitalizing a letter, I’m just not as strong with RegEx, and splitting "somethingLikeThis" into "something Like This" is where I’m having trouble.

• javascript
• regex

Share Improve this question Follow edited Aug 15, 2019 at 17:10 Sebastian Simon 19.5k88 gold badges6060 silver badges8484 bronze badges asked Nov 10, 2010 at 21:30 A Wizard Did ItA Wizard Did It 3,66444 gold badges3131 silver badges3232 bronze badges 3

• 7 How is this a duplicate of that. All that does is capitalize the first character in a string, nothing close to what I want to do. – A Wizard Did It Commented Nov 10, 2010 at 21:36
• Hmm its not a dupe of the question, but the result might be the same. Or is that not what you wanted to do ? Elaborate more ? – superfro Commented Nov 10, 2010 at 21:38
• For regex practice I suggest RegExr or Expresso to test in and just look at all the regex questions on SO and try to answer them. Regexs are not the simplest thing in the world, but just remember that if your regex is confusing YOU then split it up and work in pieces. – josh.trow Commented Nov 10, 2010 at 21:42

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12 Answers 12

Sorted by: Reset to default 480

"thisStringIsGood"
    // insert a space before all caps
    .replace(/([A-Z])/g, ' $1')
    // uppercase the first character
    .replace(/^./, function(str){ return str.toUpperCase(); })

displays

This String Is Good

(function() {

  const textbox = document.querySelector('#textbox')
  const result = document.querySelector('#result')
  function split() {
      result.innerText = textbox.value
        // insert a space before all caps
        .replace(/([A-Z])/g, ' $1')
        // uppercase the first character
        .replace(/^./, (str) => str.toUpperCase())
    };

  textbox.addEventListener('input', split);
  split();
}());

#result {
  margin-top: 1em;
  padding: .5em;
  background: #eee;
  white-space: pre;
}

<div>
  Text to split
  <input id="textbox" value="thisStringIsGood" />
</div>

<div id="result"></div>

I had an idle interest in this, particularly in handling sequences of capitals, such as in xmlHTTPRequest. The listed functions would produce "Xml H T T P Request" or "Xml HTTPRequest", mine produces "Xml HTTP Request".

function unCamelCase (str){
    return str
        // insert a space between lower & upper
        .replace(/([a-z])([A-Z])/g, '$1 $2')
        // space before last upper in a sequence followed by lower
        .replace(/\b([A-Z]+)([A-Z])([a-z])/, '$1 $2$3')
        // uppercase the first character
        .replace(/^./, function(str){ return str.toUpperCase(); })
}

There's also a String.prototype version in a gist.

This can be concisely done with regex lookahead (live demo):

function splitCamelCaseToString(s) {
    return s.split(/(?=[A-Z])/).join(' ');
}

(I thought that the g (global) flag was necessary, but oddly enough, it isn't in this particular case.)

Using lookahead with split ensures that the matched capital letter is not consumed and avoids dealing with a leading space if UpperCamelCase is something you need to deal with. To capitalize the first letter of each, you can use:

function splitCamelCaseToString(s) {
    return s.split(/(?=[A-Z])/).map(function(p) {
        return p.charAt(0).toUpperCase() + p.slice(1);
    }).join(' ');
}

The map array method is an ES5 feature, but you can still use it in older browsers with some code from MDC. Alternatively, you can iterate over the array elements using a for loop.

I think this should be able to handle consecutive uppercase characters as well as simple camelCase.

For example: someVariable => someVariable, but ABCCode != A B C Code.

The below regex works on your example but also the common example of representing abbreviations in camcelCase.

"somethingLikeThis"
    .replace(/([a-z])([A-Z])/g, '$1 $2')
    .replace(/([A-Z])([a-z])/g, ' $1$2')
    .replace(/\ +/g, ' ') => "something Like This"

"someVariableWithABCCode"
    .replace(/([a-z])([A-Z])/g, '$1 $2')
    .replace(/([A-Z])([a-z])/g, ' $1$2')
    .replace(/\ +/g, ' ') => "some Variable With ABC Code"

You could also adjust as above to capitalize the first character.

Lodash handles this nicely with _.startCase()

function spacecamel(s){
    return s.replace(/([a-z])([A-Z])/g, '$1 $2');
}

spacecamel('somethingLikeThis')

// returned value: something Like This

A solution that handles numbers as well:

function capSplit(str){
   return str.replace(
      /(^[a-z]+)|[0-9]+|[A-Z][a-z]+|[A-Z]+(?=[A-Z][a-z]|[0-9])/g,
      function(match, first){
          if (first) match = match[0].toUpperCase() + match.substr(1);
          return match + ' ';
          }
       )
   }

Tested here [JSFiddle, no library. Not tried IE]; should be pretty stable.

Try this solution here -

var value = "myCamelCaseText";
var newStr = '';
for (var i = 0; i < value.length; i++) {
  if (value.charAt(i) === value.charAt(i).toUpperCase()) {
    newStr = newStr + ' ' + value.charAt(i)
  } else {
    (i == 0) ? (newStr += value.charAt(i).toUpperCase()) : (newStr += value.charAt(i));
  }
}
return newStr;

If you don't care about older browsers (or don't mind using a fallback reduce function for them), this can split even strings like 'xmlHTTPRequest' (but certainly the likes of 'XMLHTTPRequest' cannot).

function splitCamelCase(str) {
        return str.split(/(?=[A-Z])/)
                  .reduce(function(p, c, i) {
                    if (c.length === 1) {
                        if (i === 0) {
                            p.push(c);
                        } else {
                            var last = p.pop(), ending = last.slice(-1);
                            if (ending === ending.toLowerCase()) {
                                p.push(last);
                                p.push(c);
                            } else {
                                p.push(last + c);
                            }
                        }
                    } else {
                        p.push(c.charAt(0).toUpperCase() + c.slice(1));
                    }
                    return p;
                  }, [])
                  .join(' ');
}

My version

function camelToSpace (txt) {
  return txt
    .replace(/([^A-Z]*)([A-Z]*)([A-Z])([^A-Z]*)/g, '$1 $2 $3$4')
    .replace(/ +/g, ' ')
}
camelToSpace("camelToSpaceWithTLAStuff") //=> "camel To Space With TLA Stuff"

const value = 'camelCase';
const map = {};
let index = 0;
map[index] = [];
for (let i = 0; i < value.length; i++) {
  if (i !== 0 && value[i] === value[i].toUpperCase()) {
    index = i;
    map[index] = [];
  }
  if (i === 0) {
    map[index].push(value[i].toUpperCase());
  } else {
    map[index].push(value[i]);
  }
}
let resultArray = [];
Object.keys(map).map(function (key, index) {
  resultArray = [...resultArray, ' ', ...map[key]];
  return resultArray;
});
console.log(resultArray.join(''));

Not regex, but useful to know plain and old techniques like this:

var origString = "thisString";
var newString = origString.charAt(0).toUpperCase() + origString.substring(1);

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