Slice and Splice array

Tell us what’s happening:

my code is working fine for all test cases in online browser. But when i try to submit in freecodecamp it is showing test cases failed
Your code so far

function frankenSplice(arr1, arr2, n) {
  // It's alive. It's alive!
  let ar = new Array();
  let j=0;
  let b=arr2.slice(n);
  for(let i=0;i<n;i++)
  return ar;

frankenSplice([1, 2, 3], [4, 5], 1);

Your browser information:

User Agent is: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36.

Link to the challenge:

You are returning this.

[ 4, [ 1, 2, 3 ], [ 5 ] ]

So you are actually putting them into arrays before you return them.