Trouble passing last condition - Sorted Union

Hello everyone,

I am to trying to troubleshoot the problem for why this code is not working, I feel it will be something simple but i am struggling to work out why it will not pass the final condition.

Thank you,

Your code so far

function uniteUnique(arr) {

let newArray =[];
for (let i =1; i<arguments.length; i++) {
for (let j = 0; j < arguments[i].length; j++) {
  if (arr.indexOf(arguments[i][j]) == -1) {


return arr.concat(newArray)


console.log(uniteUnique([1, 2, 3], [5, 2, 1, 4], [2, 1], [6, 7, 8]));

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User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.193 Safari/537.36.

Challenge: Sorted Union

Link to the challenge:

I solved it myself… the return statement has fooled me again! :slight_smile:

Not sure how to delete.