Why do I have to push my string into an array only to join it back again?

Question

So I want to capitalize the starting letter of each word in a string. Here's how I did it:

function LetterCapitalize(str) { 
var arr = str.split(" ");
var newArr = [];
  for(i = 0; i < arr.length; i++) {
    var newStr = arr[i].toString();
    newArr.push(newStr.substring(0,1).toUpperCase() + newStr.substring(1,newStr.length));
  }
  return newArr.join(" ");

}

This code is correct and the first letter of every word in the string was capitalized. However, when I tried to shorten my code like this, it only returned the last word of the string with the first letter capitalized, but nothing else:

function LetterCapitalize(str) { 
var arr = str.split(" ");
var newArr = [];
  for(i = 0; i < arr.length; i++) {
    var newStr = arr[i].toString();
  }
  return newStr.substring(0,1).toUpperCase() + newStr.substring(1,newStr.length);

}

Basically, what I did was remove the part where I push the new string into a new array, only to join it back into a string.

Answer 1

Problem is in the for loop part code. Here in every iteration the newstr get the value of arr[i].toString(); and the old value i.e arr[i-1].toString(); which is in newStr is overwritten. Hence only the last iteration value is stored in newStr

for(i = 0; i < arr.length; i++) {
 var newStr = arr[i].toString();
}

Try this:

function LetterCapitalize(str) { 
 var arr = str.split(" ");
 var newStr = "";  
 for(i = 0; i < arr.length; i++) {
    var temp = arr[i].toString();
    newStr =  newStr + temp.substring(0,1).toUpperCase() + temp.substring(1,temp.length)+" ";
   }
 return newStr;
}

alert(LetterCapitalize("hello i am rohit "));