Title Case a Sentence (Help)

Hi, can anyone explain why the code below not working? And i also get this error four times when i run the test : Cannot assign to read only property ‘0’ of string ‘i’m’

function titleCase(str) {
  str = str.toLowerCase();
  let arr = str.split(" ");
  let newStr = "";

  for (let i = 0; i < arr.length; i++) {
    let temp = arr[i][0].toUpperCase();
    arr[i][0] = temp.toUpperCase();
    newStr = newStr + " " + arr[i];

  return newStr;

titleCase("I'm a little tea pot");

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Link to the challenge:

I’ve edited your post for readability. When you enter a code block into a forum post, please precede it with a separate line of three backticks and follow it with a separate line of three backticks to make easier to read.

See this post to find the backtick on your keyboard. The “preformatted text” tool in the editor (</>) will also add backticks around text.

Note: Backticks are not single quotes.


It looks like you’re probably adding a space at the beginning of your newStr.

But even the first test, which is this:

titleCase(“I’m a little tea pot”)` should return a string.

is not passed with the code i wrote in the first post.

Thank you for answers guys. After learning some js methods I passed the test the way below.

function titleCase(str) {
return str.toLowerCase().split(/[^a-z']/i).map(x => (x[0].toUpperCase() + x.slice(1))).join(" ");
titleCase("I'm a little tea pot");