targeting first letters in an array for capitalization

Question

function makeTitle(str) {
let arr = str.split(' ');

  for(let i=0; i<arr.length; i++) {
    arr[i][0] = arr[i][0].toUpperCase();
  }
  return arr;
}

makeTitle("This is a title") 
  //➞ "This Is A Title"

Hey guys, why isn't this changing the first letter of every word in the array? When I console.log it, I can see it selects 'T' 'i' 'a' and 't' like its supposed to. So why doesn't it change their values?

Strings are immutable. Return the new string rather than trying to modify the old one. — evolutionxbox, May 02 '21 at 03:13
In other words you need to replace `arr[i]` with a modified string — charlietfl, May 02 '21 at 03:18
`str.split(" ").map(word => word[0].toUpperCase() + word.slice(1)).join(" ")` — Mulan, May 02 '21 at 03:21

score 0 · Accepted Answer · answered May 02 '21 at 03:19

You cannot change a string directly once it's set. Instead you can create a new string and return it. So to get this to work properly, you would get the letter change it, and then get the remaining string and join them. Then replace the value in the array. Something like this.

arr[i] = arr[i][0].toUpperCase() + arr[i].slice(1)

targeting first letters in an array for capitalization

1 Answers1