Intermediate Algorithm Scripting - Diff Two Arrays

Tell us what’s happening:
I have a doubt with the commented part
I’m unable to figure out the use of it
I want a detailed explanation of how it is working…

Your code so far

function diffArray(arr1, arr2) {
  const result = [];
  const items = new Set([...arr1, ...arr2]);
    items.forEach(item=> {
      if(!arr1.includes(item) || !arr2.includes(item)){  //Here, what is necessity of ! operator?
      return result;
console.log(diffArray([1, 2, 3, 5], [1, 2, 3, 4, 5]));

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Challenge: Intermediate Algorithm Scripting - Diff Two Arrays

Link to the challenge:

It’s easier to explain this solution if you already have a solution of your own. Can you share your solution?

If you don’t have a solution yet, I’d start there. Reading code is an important skill,when it doesn’t really help you learn how to write code.

I didn’t solved it yet!

could you please explain that specific commented part for me

No, I don’t really enjoy explaining solutions to people when they haven’t solved the problem yet. I don’t think its very productive and I honestly don’t enjoy the process.

I’d be happy to help you work on your own code for the problem though.