How come this solution is not accepted?

JavaScript
1

Tell us what’s happening:
The following code is based on a solution for the Longest Word question prior to this one. Any thoughts on why this is not acceptable? I understand it’s only one of the many ways to solve this though.

Your code so far


function largestOfFour(arr) {
for(let i=0; i<arr.length; i++) {
  let arrSet = arr[i];
  console.log("arrSet" + i, arrSet)
  let compare = (set) => {
    console.log("starting set: ", set);
    // if set only has one number left
    // splice the set
    if(set.length === 1) {
      console.log("new set (", i, "): ", set);
      return set;
    }
    // if first num is greater than
    // recursively compare the same set
    else if(set[0] >= set[1]) {
      console.log(set[0], " is greater");
      set.splice(1, 1)
      return compare(set);
    }
    // if first num is less than
    else if(set[0] <= set[1]) {
      console.log(set[1], " is greater")
      return compare(set.slice(1, set.length));
    }
  }
  arr.splice(i, 1, compare(arrSet));
}
console.log("final arr", arr);
return arr;
}

// returns [ [ 5 ], [ 27 ], [ 39 ], [ 1001 ] ]
largestOfFour([[4, 5, 1, 3], [13, 27, 18, 26], [32, 35, 37, 39], [1000, 1001, 857, 1]]);

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Challenge: Return Largest Numbers in Arrays

Link to the challenge: