Basic Data Structures: Check For The Presence of an Element With indexOf() question

JavaScript
1

Hello. I have this code:

function quickCheck(arr, elem) {
  // change code below this line
if(arr.indexOf(elem)) {
  return true;
}
else if(arr.indexOf(elem) === -1){
  return false;
}
  // change code above this line
}

// change code here to test different cases:
console.log(quickCheck(['squash', 'onions', 'shallots'], 'mushrooms'));

I get errors:

quickCheck(["squash", "onions", "shallots"], "mushrooms")

should return

false

quickCheck(["onions", "squash", "shallots"], "onions")

should return

true

quickCheck([true, false, false], undefined)

should return

false

Any ideas why my code does not work?

2

when indexOf returns 0 this will not execute because 0 is a falsy value

1 Like
3

array.indexOf(item) return index of item or -1 if item is not found
but -1 is not a falsy value in javascript
arr.indexOf(elem) is always true : your function return always true (except if item is at index 0 the function return undefined)

4

If you don’t care what the found index is, use arr.includes(item) and not indexOf. It just returns true or false as you’d expect.

5

Thanks for your replies.