Converting a string with spaces into camel case

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, '');
}

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

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();
  });
}

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

_.camelCase('Foo Bar');
// → 'fooBar'

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

_.camelCase('__FOO_BAR__');
// → 'fooBar'

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 camelCase 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 This is only for one language. For another language, you have to search and find

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('');
}

Reliable, high-performance example:

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

Case-changing characters:

• hyphen -
• underscore _
• period .
• space

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

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.

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.

To effectively create a function that converts the casing of a string to camel-case, the function will also need to convert each string to lower-case first, before transforming the casing of the first character of non-first strings to an uppercase letter.

My example string is:

"text That I WaNt to make cAMEL case"

Many other solutions provided to this question return this:

"textThatIWaNtToMakeCAMELCase"

What I believe would be the desired output would be this, though, where all the mid-string uppercase characters are first transformed to be lowercase:

"textThatIWantToMakeCamelCase"

This can be done WITHOUT using any replace() method calls, by utilizing the String.prototype.split(), Array.prototype.map(), and Array.prototype.join() methods:

≤ ES5 Version

function makeCamelCase(str) {
  return str
    .split(' ')
    .map((e,i) => i
      ? e.charAt(0).toUpperCase() + e.slice(1).toLowerCase()
      : e.toLowerCase()
    )
    .join('')
}

makeCamelCase("text That I WaNt to make cAMEL case")
// -> "textThatIWantToMakeCamelCase" ✅

I'll break down what each line does, and then provide the same solution in two other formats— ES6 and as a String.prototype method, though I'd advise against extending built-in JavaScript prototypes directly like this.

Explainer

function makeCamelCase(str) {
  return str
    // split string into array of different words by splitting at spaces
    .split(' ')
    // map array of words into two different cases, one for the first word (`i == false`) and one for all other words in the array (where `i == true`). `i` is a parameter that denotes the current index of the array item being evaluated. Because indexes start at `0` and `0` is a "falsy" value, we can use the false/else case of this ternary expression to match the first string where `i === 0`.
    .map((e,i) => i
      // for all non-first words, use a capitalized form of the first character + the lowercase version of the rest of the word (excluding the first character using the slice() method)
      ? e.charAt(0).toUpperCase() + e.slice(1).toLowerCase()
      // for the first word, we convert the entire word to lowercase
      : e.toLowerCase()
    )
    // finally, we join the different strings back together into a single string without spaces, our camel-cased string
    .join('')
}

makeCamelCase("text That I WaNt to make cAMEL case")
// -> "textThatIWantToMakeCamelCase" ✅

Condensed ES6+ (One-Liner) Version

const makeCamelCase = str => str.split(' ').map((e,i) => i ? e.charAt(0).toUpperCase() + e.slice(1).toLowerCase() : e.toLowerCase()).join('')

makeCamelCase("text That I WaNt to make cAMEL case")
// -> "textThatIWantToMakeCamelCase" ✅

String.prototype method version

String.prototype.toCamelCase = function() {
  return this
    .split(' ')
    .map((e,i) => i
      ? e.charAt(0).toUpperCase() + e.slice(1).toLowerCase()
      : e.toLowerCase()
    )
    .join('')
}

"text That I WaNt to make cAMEL case".toCamelCase()
// -> "textThatIWantToMakeCamelCase" ✅

This function by pass cammelcase such these tests

• Foo Bar
• --foo-bar--
• __FOO_BAR__-
• foo123Bar
• foo_Bar

function toCamelCase(str)
{
  var arr= str.match(/[a-z]+|\d+/gi);
  return arr.map((m,i)=>{
    let low = m.toLowerCase();
    if (i!=0){
      low = low.split('').map((s,k)=>k==0?s.toUpperCase():s).join``
    }
    return low;
  }).join``;
}
console.log(toCamelCase('Foo      Bar'));
console.log(toCamelCase('--foo-bar--'));
console.log(toCamelCase('__FOO_BAR__-'));
console.log(toCamelCase('foo123Bar'));
console.log(toCamelCase('foo_Bar'));

console.log(toCamelCase('EquipmentClass name'));
console.log(toCamelCase('Equipment className'));
console.log(toCamelCase('equipment class name'));
console.log(toCamelCase('Equipment Class Name'));

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"

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.

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

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.

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

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`);
});

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, '' );
}

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.

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());
};

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());

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');
  });
});

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;
}

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'))

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

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), '');

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

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('');
}      

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"

const toCamelCase = str =>
  str
    .replace(/[^a-zA-Z0-9]+(.)/g, (m, chr) => chr.toUpperCase())
    .replace(/^\w/, c => c.toLowerCase());