Mutations-Code Feedback for alternative solution

Tell us what’s happening:

Hi there,
I’m still struggling to bring the given solution using ‘===-1’ and the advice of moz-dev
together, where ‘!==-1’ is the way to go to check if a string exists.
I tried both solutions, but only the first one works.
The second one using moz-dev-solution doesn’t work for the first example.
Why that?
Any help is appreciated.
Thanks in advance.

Your code so far

function mutation(arr) {
  var source= arr[0].toLowerCase();
  var target= arr[1].toLowerCase();
  for(var i=0;i<target.length;i++){

mutation(["hello", "hey"]);

Your browser information:

Your Browser User Agent is: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.167 Safari/537.36.

Link to the challenge:

indexOf will only return -1 if the given string is not found in the target. !== -1 is the only way to check if something exists as === -1 asserts that it does not exist.

Hi PortableStick,
thanks for your quick reply.
Ok, so the description here is basically just wrong?

No, it’s exactly right. Pay close attention to the string values being used.

1 Like

:smiley: Ok, I think i got your point now. Thanks for your help.
So if I still want to use my first solution this modification will do the job:

      return false; 


Well, there’s another reason why the solution you posted isn’t going to work and it has nothing to do with indexOf. When you return inside of a loop, it exits the function. So if you don’t have any if statements in your loop, it’s just going to exit out before i ever increments.

But why do this…

if((source.indexOf(target[i])!==-1)===false) return false

… when you could do this?

if(source.indexOf(target[i]) === -1) return false

Don’t make statements more complicated than they have to be!

1 Like

Ok, many thanks for the clarification.

I totally agree with what you are saying. It was just for the purpose of demonstrating and to show that I now understand why my code didn’t work earlier.


  *******Mutations (my solution)********

function mutation(arr) {

var x = arr[0].toLowerCase().split(’’);

var y = arr[1].toLowerCase().split(’’);

return y.every(function(val){

return x.includes(val) ;