Mutations code always returns true

JavaScript
1

Can anyone help me out? I pass all the True test cases, but none of the false cases.

function mutation(arr) {

  let word1 = arr[0].toLowerCase();
  let word2 = arr[1].toLowerCase().split("");

  word2.forEach(function(i){
    if(word1.indexOf(i) < 0)
    {
      return false;
    }
    
  })

 return true;
}

mutation(["hello", "hey"]);
3

Got it, thanks! @camperextraordinaire I tried to be a little fancy with forEach. I guess I need to stick to the basics, lol.