Convert hyphens to camel case (camelCase)

Question

With regex (i assume) or some other method, how can i convert things like:

marker-image or my-example-setting to markerImage or myExampleSetting.

I was thinking about just splitting by - then convert the index of that hypen +1 to uppercase. But it seems pretty dirty and was hoping for some help with regex that could make the code cleaner.

No jQuery...

Answer 1

Try this:

var camelCased = myString.replace(/-([a-z])/g, function (g) { return g[1].toUpperCase(); });

The regular expression will match the -i in marker-image and capture only the i. This is then uppercased in the callback function and replaced.

Answer 2

This is one of the great utilities that Lodash offers if you are enlightened and have it included in your project.

var str = 'my-hyphen-string';
str = _.camelCase(str);
// results in 'myHyphenString'

Answer 3

You can get the hypen and the next character and replace it with the uppercased version of the character:

var str="marker-image-test";
str.replace(/-([a-z])/g, function (m, w) {
    return w.toUpperCase();
});

Answer 4

Here's my version of camelCase function:

var camelCase = (function () {
    var DEFAULT_REGEX = /[-_]+(.)?/g;

    function toUpper(match, group1) {
        return group1 ? group1.toUpperCase() : '';
    }
    return function (str, delimiters) {
        return str.replace(delimiters ? new RegExp('[' + delimiters + ']+(.)?', 'g') : DEFAULT_REGEX, toUpper);
    };
})();

It handles all of the following edge cases:

• takes care of both underscores and hyphens by default (configurable with second parameter)
• string with unicode characters
• string that ends with hyphens or underscore
• string that has consecutive hyphens or underscores

Here's a link to live tests: http://jsfiddle.net/avKzf/2/

Here are results from tests:

• input: "ab-cd-ef", result: "abCdEf"
• input: "ab-cd-ef-", result: "abCdEf"
• input: "ab-cd-ef--", result: "abCdEf"
• input: "ab-cd--ef--", result: "abCdEf"
• input: "--ab-cd--ef--", result: "AbCdEf"
• input: "--ab-cd-__-ef--", result: "AbCdEf"

Notice that strings that start with delimiters will result in a uppercase letter at the beginning. If that is not what you would expect, you can always use lcfirst. Here's my lcfirst if you need it:

function lcfirst(str) {
    return str && str.charAt(0).toLowerCase() + str.substring(1);
}

Answer 5

Use String's replace() method with a regular expression literal and a replacement function.

For example:

'uno-due-tre'.replace(/-./g, (m) => m[1].toUpperCase()) // --> 'unoDueTre'

Explanation:

• 'uno-due-tre' is the (input) string that you want to convert to camel case.
• /-./g (the first argument passed to replace()) is a regular expression literal.
  • The '-.' (between the slashes) is a pattern. It matches a single '-' character followed by any single character. So for the string 'uno-due-tre', the pattern '-.' matches '-d' and '-t' .
  • The 'g' (after the closing slash) is a flag. It stands for "global" and tells replace() to perform a global search and replace, ie, to replace all matches, not just the first one.
• (m) => m[1].toUpperCase() (the second argument passed to replace()) is the replacement function. It's called once for each match. Each matched substring is replaced by the string this function returns. m (the first argument of this function) represents the matched substring. This function returns the second character of m uppercased. So when m is '-d', this function returns 'D'.
• 'unoDueTre' is the new (output) string returned by replace(). The input string is left unchanged.

Answer 6

This doesn't scream out for a RegExp to me. Personally I try to avoid regular expressions when simple string and array methods will suffice:

let upFirst = word => 
  word[0].toUpperCase() + word.toLowerCase().slice(1)

let camelize = text => {
  let words = text.split(/[-_]/g) // ok one simple regexp.
  return words[0].toLowerCase() + words.slice(1).map(upFirst)
}

camelize('marker-image') // markerImage

Answer 7

Here is my implementation (just to make hands dirty)

/**
 * kebab-case to UpperCamelCase
 * @param {String} string
 * @return {String}
 */
function toUpperCamelCase(string) {
  return string
    .toLowerCase()
    .split('-')
    .map(it => it.charAt(0).toUpperCase() + it.substring(1))
    .join('');
}

Answer 8

// Turn the dash separated variable name into camelCase.
str = str.replace(/\b-([a-z])/g, (_, char) => char.toUpperCase());

Answer 9

Here is another option that combines a couple answers here and makes it method on a string:

if (typeof String.prototype.toCamel !== 'function') {
  String.prototype.toCamel = function(){
    return this.replace(/[-_]([a-z])/g, function (g) { return g[1].toUpperCase(); })
  };
}

Used like this:

'quick_brown'.toCamel(); // quickBrown
'quick-brown'.toCamel(); // quickBrown

Answer 10

Another take.

Used when...

var string = "hyphen-delimited-to-camel-case"
or
var string = "snake_case_to_camel_case"


function toCamelCase( string ){
  return string.toLowerCase().replace(/(_|-)([a-z])/g, toUpperCase );
}

function toUpperCase( string ){
  return string[1].toUpperCase();
}

Output: hyphenDelimitedToCamelCase

Answer 11

is also possible use indexOf with recursion for that task.

input some-foo_sd_dsd-weqe
output someFooSdDsdWeqe

comparison ::: measure execution time for two different scripts:

$ node camelCased.js
someFooSdDsdWeqe
test1: 2.986ms
someFooSdDsdWeqe
test2: 0.231ms

code:

console.time('test1');
function camelCased (str) {

        function check(symb){

            let idxOf = str.indexOf(symb);
            if (idxOf === -1) {
                return str;
            }

            let letter = str[idxOf+1].toUpperCase();
            str = str.replace(str.substring(idxOf+1,idxOf+2), '');
            str = str.split(symb).join(idxOf !== -1 ? letter : '');

            return camelCased(str);
        }       

        return check('_') && check('-');

    }

console.log(camelCased ('some-foo_sd_dsd-weqe'));
console.timeEnd('test1');



console.time('test2');

    function camelCased (myString){
     return myString.replace(/(-|\_)([a-z])/g, function (g) { return  g[1].toUpperCase(); });
   }


console.log(camelCased ('some-foo_sd_dsd-weqe'));
console.timeEnd('test2');

Answer 12

Just a version with flag, for loop and without Regex:

function camelCase(dash) { 

  var camel = false;
  var str = dash;
  var camelString = '';

  for(var i = 0; i < str.length; i++){
    if(str.charAt(i) === '-'){
      camel = true;

    } else if(camel) {
      camelString += str.charAt(i).toUpperCase();
      camel = false;
    } else {
      camelString += str.charAt(i);
    }
  } 
  return camelString;
}

Answer 13

You can use camelcase from NPM.

npm install --save camelcase

const camelCase = require('camelcase');
camelCase('marker-image'); // => 'markerImage';
camelCase('my-example-setting'); // => 'myExampleSetting';

Answer 14

Use this if you allow numbers in your string.

Obviously the parts that begin with a number will not be capitalized, but this might be useful in some situations.

function fromHyphenToCamelCase(str) {
  return str.replace(/-([a-z0-9])/g, (g) => g[1].toUpperCase())
}

function fromHyphenToCamelCase(str) {
  return str.replace(/-([a-z0-9])/g, (g) => g[1].toUpperCase())
}

const str1 = "category-123";
const str2 = "111-222";
const str3 = "a1a-b2b";
const str4 = "aaa-2bb";

console.log(`${str1} => ${fromHyphenToCamelCase(str1)}`);
console.log(`${str2} => ${fromHyphenToCamelCase(str2)}`);
console.log(`${str3} => ${fromHyphenToCamelCase(str3)}`);
console.log(`${str4} => ${fromHyphenToCamelCase(str4)}`);

Answer 15

You can also use string and array methods; I used trim to avoid any spaces.

const properCamel = (str) =>{

  const lowerTrim = str.trim().toLowerCase(); 

  const array = lowerTrim.split('-');

  const firstWord = array.shift();

  const caps = array.map(word=>{

    return word[0].toUpperCase() + word.slice(1);

  })

  caps.unshift(firstWord)

  return caps.join('');

}

Answer 16

This simple solution takes into account these edge cases.

• Single word
• Single letter
• No hyphen
• More than 1 hyphen

const toCamelCase = (text) => text.replace(/(.)([^-|$]*)[-]*/g, (_,letter,word) => `${letter.toUpperCase()}${word.toLowerCase()}`)