Converting Odd and Even-indexed characters in a string to uppercase/lowercase in Javascript?

Question

I need to make a function that reads a string input and converts the odd indexed characters in the string to upperCase and the even ones to lowerCase.

function alternativeCase(string){
    for(var i = 0; i < string.length; i++){
        if (i % 2 != 0) {
            string[i].toUpperCase();
        }
        else {
            string[i].toLowerCase();
        }   
    }
    return string;
}

How to fix my code?

Answer 1

Try this:

function alternativeCase(string){
    var output = "";
    for(var i = 0; i < string.length; i++){
        if (i % 2 != 0) {
            output += string[i].toUpperCase();
        }
        else {
            output += string[i].toLowerCase();
         }   
    }
    return output;
}

Answer 2

Strings in JavaScript are immutable, Try this instead:

function alternativeCase(string){
     var newString = [];
     for(var i = 0; i < string.length; i++){
        if (i % 2 != 0) {
           newString[i] = string[i].toUpperCase();
        }
        else {
           newString[i] = string[i].toLowerCase();
        }   
     }
   return newString.join('');
}

Answer 3

function alternativeCase(string){
  return string.split('').map(function(c,i) {
    return i & 1 ? c.toUpperCase() : c.toLowerCase();
  }).join('');
}

---

Update 2019

These days it's pretty safe to use ES6 syntax:

const alternativeCase = string => string.split('')
  .map((c,i) => i & 1 ? c.toUpperCase() : c.toLowerCase()).join('');

Answer 4

RegExp alternative that handles space between characters :

const alternativeCase = s => s.replace(/(\S\s*)(\S?)/g, (m, a, b) => a.toUpperCase() + b.toLowerCase());

console.log( alternativeCase('alternative Case') )