Mutations: why doesn't it work without 'if' statement?

Hey guys, I don’t really know why my code isn’t working. It looks like it only checks the first character of the second element of ‘arr’, despite me using the ‘for loop’. I checked a couple of solutions and was able to make mine work with ‘if’ statement but still don’t understand why isn’t this a correct solution. Please help me find the problem, all comments are appreciated!

Your code so far

function mutation(arr) {
  var arr0 = arr[0].toLowerCase();
  var arr1 = arr[1].toLowerCase().split('');
  var i;
  for (i = 0; i < arr1.length; i++) {
       return (arr0.indexOf(arr1[i]) >= 0);

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

Your browser information:

Your Browser User Agent is: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.94 Safari/537.36.

Link to the challenge:

You’ve got a return statement in your for loop. It’s exiting the function immediately. You’ll need to use an if statement to check whether or not you should be returning.

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