Mutations - How to get rid of duplicate elements in an array

Hello! I am working on the freeCodeCamp challenge “Mutations”, and I’m not sure how to remove duplicate elements in an array. I tried to use function alpha(arr) to check each element against each other element next to each other (since I already alphabetized the array) but it is throwing an infinite loop. Is this the right way to go about this?

My code so far

  var zero = arr[0].toLowerCase();
  var one = arr[1].toLowerCase();
  var zeroarr = zero.split("");
  var onearr = one.split("");
  function alpha(arr) {
    for(x = 0; x !== arr.size; x++) {
      if(arr[x] == arr[x + 1]) {
        arr.splice(x, 1);
  var zerostring = zeroarr.toString();
  var onestring = onearr.toString();
  return zerostring.indexOf(onestring) !== -1;

mutation(["Mary", "Aarmy"]);

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Link to the challenge:

Hey James,

Your for loop is infinite here because you meant to use .length instead of .size in the for loop.

Pro tip: don’t modify an array that you’re iterating over. It is a classic way to get unexpected results and infinite loops.

Thanks! this helped a lot!