Converting any string into camel case

How can I convert a string into camel case using javascript regex?

EquipmentClass name or Equipment className or equipment class name or Equipment Class Name

should all become: equipmentClassName.

Answers:

Answer

Looking at your code, you can achieve it with only two replace calls:

function camelize(str) {
  return str.replace(/(?:^\w|[A-Z]|\b\w)/g, function(word, index) {
    return index === 0 ? word.toLowerCase() : word.toUpperCase();
  }).replace(/\s+/g, '');
}

camelize("EquipmentClass name");
camelize("Equipment className");
camelize("equipment class name");
camelize("Equipment Class Name");
// all output "equipmentClassName"

Edit: Or in with a single replace call, capturing the white spaces also in the RegExp.

function camelize(str) {
  return str.replace(/(?:^\w|[A-Z]|\b\w|\s+)/g, function(match, index) {
    if (+match === 0) return ""; // or if (/\s+/.test(match)) for white spaces
    return index === 0 ? match.toLowerCase() : match.toUpperCase();
  });
}
Answer

I just ended up doing this:

String.prototype.toCamelCase = function(str) {
    return str
        .replace(/\s(.)/g, function($1) { return $1.toUpperCase(); })
        .replace(/\s/g, '')
        .replace(/^(.)/, function($1) { return $1.toLowerCase(); });
}

I was trying to avoid chaining together multiple replace statements. Something where I'd have $1, $2, $3 in my function. But that type of grouping is hard to understand, and your mention about cross browser problems is something I never thought about as well.

Answer

In Scott’s specific case I’d go with something like:

String.prototype.toCamelCase = function() {
    return this.replace(/^([A-Z])|\s(\w)/g, function(match, p1, p2, offset) {
        if (p2) return p2.toUpperCase();
        return p1.toLowerCase();        
    });
};

'EquipmentClass name'.toCamelCase()  // -> equipmentClassName
'Equipment className'.toCamelCase()  // -> equipmentClassName
'equipment class name'.toCamelCase() // -> equipmentClassName
'Equipment Class Name'.toCamelCase() // -> equipmentClassName

The regex will match the first character if it starts with a capital letter, and any alphabetic character following a space, i.e. 2 or 3 times in the specified strings.

By spicing up the regex to /^([A-Z])|[\s-_](\w)/g it will also camelize hyphen and underscore type names.

'hyphen-name-format'.toCamelCase()     // -> hyphenNameFormat
'underscore_name_format'.toCamelCase() // -> underscoreNameFormat
Answer

If regexp isn't required, you might want to look at following code I made a long time ago for Twinkle:

String.prototype.toUpperCaseFirstChar = function() {
    return this.substr( 0, 1 ).toUpperCase() + this.substr( 1 );
}

String.prototype.toLowerCaseFirstChar = function() {
    return this.substr( 0, 1 ).toLowerCase() + this.substr( 1 );
}

String.prototype.toUpperCaseEachWord = function( delim ) {
    delim = delim ? delim : ' ';
    return this.split( delim ).map( function(v) { return v.toUpperCaseFirstChar() } ).join( delim );
}

String.prototype.toLowerCaseEachWord = function( delim ) {
    delim = delim ? delim : ' ';
    return this.split( delim ).map( function(v) { return v.toLowerCaseFirstChar() } ).join( delim );
}

I haven't made any performance tests, and regexp versions might or might not be faster.

Answer

My ES6 approach:

const camelCase = str => {
  let string = str.toLowerCase().replace(/[^A-Za-z0-9]/g, ' ').split(' ')
                  .reduce((result, word) => result + capitalize(word.toLowerCase()))
  return string.charAt(0).toLowerCase() + string.slice(1)
}

const capitalize = str => str.charAt(0).toUpperCase() + str.toLowerCase().slice(1)

let baz = 'foo bar'
let camel = camelCase(baz)
console.log(camel)  // "fooBar"
camelCase('foo bar')  // "fooBar"
camelCase('FOO BAR')  // "fooBar"
camelCase('x nN foo bar')  // "xNnFooBar"
camelCase('!--foo-¿?-bar--121-**%')  // "fooBar121"
Answer

Reliable working example that I've been using for years:

function camelize(text) {
    text = text.replace(/[-_\s.]+(.)?/g, (_, c) => c ? c.toUpperCase() : '');
    return text.substr(0, 1).toLowerCase() + text.substr(1);
}

Case-changing characters include:

  • hyphen
  • underscore
  • period
  • space
Answer

following @Scott's readable approach, a little bit of fine tuning

// convert any string to camelCase
var toCamelCase = function(str) {
  return str.toLowerCase()
    .replace( /['"]/g, '' )
    .replace( /\W+/g, ' ' )
    .replace( / (.)/g, function($1) { return $1.toUpperCase(); })
    .replace( / /g, '' );
}
Answer

All 14 permutations below produce the same result of "equipmentClassName".

String.prototype.toCamelCase = function() {
  return this.replace(/[^a-z ]/ig, '')  // Replace everything but letters and spaces.
    .replace(/(?:^\w|[A-Z]|\b\w|\s+)/g, // Find non-words, uppercase letters, leading-word letters, and multiple spaces.
      function(match, index) {
        return +match === 0 ? "" : match[index === 0 ? 'toLowerCase' : 'toUpperCase']();
      });
}

String.toCamelCase = function(str) {
  return str.toCamelCase();
}

var testCases = [
  "equipment class name",
  "equipment class Name",
  "equipment Class name",
  "equipment Class Name",
  "Equipment class name",
  "Equipment class Name",
  "Equipment Class name",
  "Equipment Class Name",
  "equipment className",
  "equipment ClassName",
  "Equipment ClassName",
  "equipmentClass name",
  "equipmentClass Name",
  "EquipmentClass Name"
];

for (var i = 0; i < testCases.length; i++) {
  console.log(testCases[i].toCamelCase());
};

Answer

little modified Scott's answer:

toCamelCase = (string) ->
  string
    .replace /[\s|_|-](.)/g, ($1) -> $1.toUpperCase()
    .replace /[\s|_|-]/g, ''
    .replace /^(.)/, ($1) -> $1.toLowerCase()

now it replaces '-' and '_' too.

Answer

There is my solution:

const toCamelWord = (word, idx) =>
  idx === 0 ?
  word.toLowerCase() :
  word.charAt(0).toUpperCase() + word.slice(1).toLowerCase();

const toCamelCase = text =>
  text
  .split(/[_-\s]+/)
  .map(toCamelWord)
  .join("");

console.log(toCamelCase('User ID'))

Answer

This method seems to outperform most answers on here, it's a little bit hacky though, no replaces, no regex, simply building up a new string that's camelCase.

String.prototype.camelCase = function(){
    var newString = '';
    var lastEditedIndex;
    for (var i = 0; i < this.length; i++){
        if(this[i] == ' ' || this[i] == '-' || this[i] == '_'){
            newString += this[i+1].toUpperCase();
            lastEditedIndex = i+1;
        }
        else if(lastEditedIndex !== i) newString += this[i].toLowerCase();
    }
    return newString;
}
Answer

This builds on the answer by CMS by removing any non-alphabetic characters including underscores, which \w does not remove.

function toLowerCamelCase(str) {
    return str.replace(/[^A-Za-z0-9]/g, ' ').replace(/^\w|[A-Z]|\b\w|\s+/g, function (match, index) {
        if (+match === 0 || match === '-' || match === '.' ) {
            return ""; // or if (/\s+/.test(match)) for white spaces
        }
        return index === 0 ? match.toLowerCase() : match.toUpperCase();
    });
}

toLowerCamelCase("EquipmentClass name");
toLowerCamelCase("Equipment className");
toLowerCamelCase("equipment class name");
toLowerCamelCase("Equipment Class Name");
toLowerCamelCase("Equipment-Class-Name");
toLowerCamelCase("Equipment_Class_Name");
toLowerCamelCase("Equipment.Class.Name");
toLowerCamelCase("Equipment/Class/Name");
// All output e
Answer

Upper camel case ("TestString") to lower camel case ("testString") without using regex (let's face it, regex is evil):

'TestString'.split('').reduce((t, v, k) => t + (k === 0 ? v.toLowerCase() : v), '');
Answer

I ended up crafting a slightly more aggressive solution:

function toCamelCase(str) {
  const [first, ...acc] = str.replace(/[^\w\d]/g, ' ').split(/\s+/);
  return first.toLowerCase() + acc.map(x => x.charAt(0).toUpperCase() 
    + x.slice(1).toLowerCase()).join('');
}

This one, above, will remove all non-alphanumeric characters and lowercase parts of words that would otherwise remain uppercased, e.g.

  • Size (comparative) => sizeComparative
  • GDP (official exchange rate) => gdpOfficialExchangeRate
  • hello => hello
Answer
const toCamelCase = str =>
  str
    .replace(/[^a-zA-Z0-9]+(.)/g, (m, chr) => chr.toUpperCase())
    .replace(/^\w/, c => c.toLowerCase());
Answer

Basic approach would be to split the string with a regex matching upper-case or spaces. Then you'd glue the pieces back together. Trick will be dealing with the various ways regex splits are broken/weird across browsers. There's a library or something that somebody wrote to fix those problems; I'll look for it.

here's the link: http://blog.stevenlevithan.com/archives/cross-browser-split

Answer

If anyone is using lodash, there is a _.camelCase() function.

_.camelCase('Foo Bar');
// ? 'fooBar'

_.camelCase('--foo-bar--');
// ? 'fooBar'

_.camelCase('__FOO_BAR__');
// ? 'fooBar'
Answer

You can use this solution :

function toCamelCase(str){
  return str.split(' ').map(function(word,index){
    // If it is the first word make sure to lowercase all the chars.
    if(index == 0){
      return word.toLowerCase();
    }
    // If it is not the first word only upper case the first char and lowercase the rest.
    return word.charAt(0).toUpperCase() + word.slice(1).toLowerCase();
  }).join('');
}
Answer

To get camelCase

ES5

var camalize = function camalize(str) {
    return str.toLowerCase().replace(/[^a-zA-Z0-9]+(.)/g, function(match, chr)
    {
        return chr.toUpperCase();
    });
}

ES6

var camalize = function camalize(str) {
    return str.toLowerCase().replace(/[^a-zA-Z0-9]+(.)/g, (m, chr) => chr.toUpperCase());
}


To get CamelSentenceCase or PascalCase

var camelSentence = function camelSentence(str) {
    return  (" " + str).toLowerCase().replace(/[^a-zA-Z0-9]+(.)/g, function(match, chr)
    {
        return chr.toUpperCase();
    });
}

Note :
For those language with accents. Do include À-ÖØ-öø-ÿ with the regex as following
.replace(/[^a-zA-ZÀ-ÖØ-öø-ÿ0-9]+(.)/g

Answer
function toCamelCase(str) {
  // Lower cases the string
  return str.toLowerCase()
    // Replaces any - or _ characters with a space 
    .replace( /[-_]+/g, ' ')
    // Removes any non alphanumeric characters 
    .replace( /[^\w\s]/g, '')
    // Uppercases the first character in each group immediately following a space 
    // (delimited by spaces) 
    .replace( / (.)/g, function($1) { return $1.toUpperCase(); })
    // Removes spaces 
    .replace( / /g, '' );
}

I was trying to find a JavaScript function to camelCase a string, and wanted to make sure special characters would be removed (and I had trouble understanding what some of the answers above were doing). This is based on c c young's answer, with added comments and the removal of $peci&l characters.

Answer

lodash can do the trick sure and well:

var _ = require('lodash');
var result = _.camelCase('toto-ce héros') 
// result now contains "totoCeHeros"

Although lodash may be a "big" library (~4kB), it contains a lot of functions that you'd normally use a snippet for, or build yourself.

Answer

Here is a one liner doing the work:

const camelCaseIt = string => string.toLowerCase().trim().split(/[.\-_\s]/g).reduce((string, word) => string + word[0].toUpperCase() + word.slice(1));

It splits the lower-cased string based on the list of characters provided in the RegExp [.\-_\s] (add more inside the []!) and returns a word array . Then, it reduces the array of strings to one concatenated string of words with uppercased first letters. Because the reduce has no initial value, it will start uppercasing first letters starting with the second word.

If you want PascalCase, just add an initial empty string ,'') to the reduce method.

Answer
return "hello world".toLowerCase().replace(/(?:(^.)|(\s+.))/g, function(match) {
    return match.charAt(match.length-1).toUpperCase();
}); // HelloWorld
Answer

you can use this solution:

String.prototype.toCamelCase = function(){
  return this.replace(/\s(\w)/ig, function(all, letter){return letter.toUpperCase();})
             .replace(/(^\w)/, function($1){return $1.toLowerCase()});
};

console.log('Equipment className'.toCamelCase());

Answer

Because this question needed yet another answer...

I tried several of the previous solutions, and all of them had one flaw or another. Some didn't remove punctuation; some didn't handle cases with numbers; some didn't handle multiple punctuations in a row.

None of them handled a string like a1 2b. There's no explicitly defined convention for this case, but some other stackoverflow questions suggested separating the numbers with an underscore.

I doubt this is the most performant answer (three regex passes through the string, rather than one or two), but it passes all the tests I can think of. To be honest, though, I really can't imagine a case where you're doing so many camel-case conversions that performance would matter.

(I added this as an npm package. It also includes an optional boolean parameter to return Pascal Case instead of Camel Case.)

const underscoreRegex = /(?:[^\w\s]|_)+/g,
    sandwichNumberRegex = /(\d)\s+(?=\d)/g,
    camelCaseRegex = /(?:^\s*\w|\b\w|\W+)/g;

String.prototype.toCamelCase = function() {
    if (/^\s*_[\s_]*$/g.test(this)) {
        return '_';
    }

    return this.replace(underscoreRegex, ' ')
        .replace(sandwichNumberRegex, '$1_')
        .replace(camelCaseRegex, function(match, index) {
            if (/^\W+$/.test(match)) {
                return '';
            }

            return index == 0 ? match.trimLeft().toLowerCase() : match.toUpperCase();
        });
}

Test cases (Jest)

test('Basic strings', () => {
    expect(''.toCamelCase()).toBe('');
    expect('A B C'.toCamelCase()).toBe('aBC');
    expect('aB c'.toCamelCase()).toBe('aBC');
    expect('abc      def'.toCamelCase()).toBe('abcDef');
    expect('abc__ _ _def'.toCamelCase()).toBe('abcDef');
    expect('abc__ _ d_ e _ _fg'.toCamelCase()).toBe('abcDEFg');
});

test('Basic strings with punctuation', () => {
    expect(`a'b--d -- f.h`.toCamelCase()).toBe('aBDFH');
    expect(`...a...def`.toCamelCase()).toBe('aDef');
});

test('Strings with numbers', () => {
    expect('12 3 4 5'.toCamelCase()).toBe('12_3_4_5');
    expect('12 3 abc'.toCamelCase()).toBe('12_3Abc');
    expect('ab2c'.toCamelCase()).toBe('ab2c');
    expect('1abc'.toCamelCase()).toBe('1abc');
    expect('1Abc'.toCamelCase()).toBe('1Abc');
    expect('abc 2def'.toCamelCase()).toBe('abc2def');
    expect('abc-2def'.toCamelCase()).toBe('abc2def');
    expect('abc_2def'.toCamelCase()).toBe('abc2def');
    expect('abc1_2def'.toCamelCase()).toBe('abc1_2def');
    expect('abc1 2def'.toCamelCase()).toBe('abc1_2def');
    expect('abc1 2   3def'.toCamelCase()).toBe('abc1_2_3def');
});

test('Oddball cases', () => {
    expect('_'.toCamelCase()).toBe('_');
    expect('__'.toCamelCase()).toBe('_');
    expect('_ _'.toCamelCase()).toBe('_');
    expect('\t_ _\n'.toCamelCase()).toBe('_');
    expect('_a_'.toCamelCase()).toBe('a');
    expect('\''.toCamelCase()).toBe('');
    expect(`\tab\tcd`.toCamelCase()).toBe('abCd');
    expect(`
ab\tcd\r

-_

|'ef`.toCamelCase()).toBe(`abCdEf`);
});
Answer
function convertStringToCamelCase(str){
    return str.split(' ').map(function(item, index){
        return index !== 0 
            ? item.charAt(0).toUpperCase() + item.substr(1) 
            : item.charAt(0).toLowerCase() + item.substr(1);
    }).join('');
}      
Answer

Here's my suggestion:

function toCamelCase(string) {
  return `${string}`
    .replace(new RegExp(/[-_]+/, 'g'), ' ')
    .replace(new RegExp(/[^\w\s]/, 'g'), '')
    .replace(
      new RegExp(/\s+(.)(\w+)/, 'g'),
      ($1, $2, $3) => `${$2.toUpperCase() + $3.toLowerCase()}`
    )
    .replace(new RegExp(/\s/, 'g'), '')
    .replace(new RegExp(/\w/), s => s.toLowerCase());
}

or

String.prototype.toCamelCase = function() {
  return this
    .replace(new RegExp(/[-_]+/, 'g'), ' ')
    .replace(new RegExp(/[^\w\s]/, 'g'), '')
    .replace(
      new RegExp(/\s+(.)(\w+)/, 'g'),
      ($1, $2, $3) => `${$2.toUpperCase() + $3.toLowerCase()}`
    )
    .replace(new RegExp(/\s/, 'g'), '')
    .replace(new RegExp(/\w/), s => s.toLowerCase());
};

Test cases:

describe('String to camel case', function() {
  it('should return a camel cased string', function() {
    chai.assert.equal(toCamelCase('foo bar'), 'fooBar');
    chai.assert.equal(toCamelCase('Foo Bar'), 'fooBar');
    chai.assert.equal(toCamelCase('fooBar'), 'fooBar');
    chai.assert.equal(toCamelCase('FooBar'), 'fooBar');
    chai.assert.equal(toCamelCase('--foo-bar--'), 'fooBar');
    chai.assert.equal(toCamelCase('__FOO_BAR__'), 'fooBar');
    chai.assert.equal(toCamelCase('!--foo-¿?-bar--121-**%'), 'fooBar121');
  });
});
Answer

I know this is an old answer, but this handles both whitespace and _ (lodash)

function toCamelCase(s){
    return s
          .replace(/_/g, " ")
          .replace(/\s(.)/g, function($1) { return $1.toUpperCase(); })
          .replace(/\s/g, '')
          .replace(/^(.)/, function($1) { return $1.toLowerCase(); });
}

console.log(toCamelCase("Hello world");
console.log(toCamelCase("Hello_world");

// Both print "helloWorld"
Answer

EDIT: Now working in IE8 without changes.

EDIT: I was in the minority about what camelCase actually is (Leading character lowercase vs. uppercase.). The community at large believes a leading lowercase is camel case and a leading capital is pascal case. I have created two functions that use regex patterns only. :) So we use a unified vocabulary I have changed my stance to match the majority.


All I believe you need is a single regex in either case:

var camel = " THIS is camel case "
camel = $.trim(camel)
    .replace(/[^A-Za-z]/g,' ') /* clean up non-letter characters */
    .replace(/(.)/g, function(a, l) { return l.toLowerCase(); })
    .replace(/(\s.)/g, function(a, l) { return l.toUpperCase(); })
    .replace(/[^A-Za-z\u00C0-\u00ff]/g,'');
// Returns "thisIsCamelCase"

or

var pascal = " this IS pascal case "
pascal = $.trim(pascal)
  .replace(/[^A-Za-z]/g,' ') /* clean up non-letter characters */
  .replace(/(.)/g, function(a, l) { return l.toLowerCase(); })
  .replace(/(^.|\s.)/g, function(a, l) { return l.toUpperCase(); })
  .replace(/[^A-Za-z\u00C0-\u00ff]/g,'');
// Returns "ThisIsPascalCase"

In functions: You will notice that in these functions the replace is swapping any non a-z with a space vs an empty string. This is to create word boundaries for capitalization. "hello-MY#world" -> "HelloMyWorld"

// remove \u00C0-\u00ff] if you do not want the extended letters like é
function toCamelCase(str) {
    var retVal = '';

    retVal = $.trim(str)
      .replace(/[^A-Za-z]/g, ' ') /* clean up non-letter characters */
      .replace(/(.)/g, function (a, l) { return l.toLowerCase(); })
      .replace(/(\s.)/g, function (a, l) { return l.toUpperCase(); })
      .replace(/[^A-Za-z\u00C0-\u00ff]/g, '');

    return retVal
}

function toPascalCase(str) {
    var retVal = '';

    retVal = $.trim(str)
      .replace(/[^A-Za-z]/g, ' ') /* clean up non-letter characters */
      .replace(/(.)/g, function (a, l) { return l.toLowerCase(); })
      .replace(/(^.|\s.)/g, function (a, l) { return l.toUpperCase(); })
      .replace(/[^A-Za-z\u00C0-\u00ff]/g, '');

    return retVal
}

Notes:

  • I left A-Za-z vs adding the case insensitivity flag (i) to the pattern (/[^A-Z]/ig) for readability.
  • This works in IE8 (srsly, who uses IE8 anymore.) Using the (F12) dev tools I have tested in IE11, IE10, IE9, IE8, IE7 and IE5. Works in all document modes.
  • This will correctly case the first letter of strings starting with or without whitespace.

Enjoy

Answer

I think this should work..

function cammelCase(str){
    let arr = str.split(' ');
    let words = arr.filter(v=>v!='');
    words.forEach((w, i)=>{
        words[i] = w.replace(/\w\S*/g, function(txt){
            return txt.charAt(0).toUpperCase() + txt.substr(1);
        });
    });
    return words.join('');
}
Answer

The top answer is terse but it doesn't handle all edge cases. For anyone needing a more robust utility, without any external dependencies:

function camelCase(str) {
    return (str.slice(0, 1).toLowerCase() + str.slice(1))
      .replace(/([-_ ]){1,}/g, ' ')
      .split(/[-_ ]/)
      .reduce((cur, acc) => {
        return cur + acc[0].toUpperCase() + acc.substring(1);
      });
}

function sepCase(str, sep = '-') {
    return str
      .replace(/[A-Z]/g, (letter, index) => {
        const lcLet = letter.toLowerCase();
        return index ? sep + lcLet : lcLet;
      })
      .replace(/([-_ ]){1,}/g, sep)
}

// All will return 'fooBarBaz'
console.log(camelCase('foo_bar_baz'))
console.log(camelCase('foo-bar-baz'))
console.log(camelCase('foo_bar--baz'))
console.log(camelCase('FooBar  Baz'))
console.log(camelCase('FooBarBaz'))
console.log(camelCase('fooBarBaz'))

// All will return 'foo-bar-baz'
console.log(sepCase('fooBarBaz'));
console.log(sepCase('FooBarBaz'));
console.log(sepCase('foo-bar-baz'));
console.log(sepCase('foo_bar_baz'));
console.log(sepCase('foo___ bar -baz'));
console.log(sepCase('foo-bar-baz'));

// All will return 'foo__bar__baz'
console.log(sepCase('fooBarBaz', '__'));
console.log(sepCase('foo-bar-baz', '__'));

Demo here: https://codesandbox.io/embed/admiring-field-dnm4r?fontsize=14&hidenavigation=1&theme=dark

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