Can someone explain what -1 represents here?

JavaScript
1

Does it mean that it will work for any positive number? Why will ‘false’ not work in it’s place?

Thanks for the help.


function filteredArray(arr, elem) {
let newArr = [];
// change code below this line
for (let i = 0; i < arr.length; i++) {
if(arr[i].indexOf(elem) == -1) {
  newArr.push(arr[i])
}
}
// change code above this line
return newArr;
}

// change code here to test different cases:
console.log(filteredArray([[3, 2, 3], [1, 6, 3], [3, 13, 26], [19, 3, 9]], 3));

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Challenge: Iterate Through All an Array’s Items Using For Loops

Link to the challenge:
https://www.freecodecamp.org/learn/javascript-algorithms-and-data-structures/basic-data-structures/iterate-through-all-an-arrays-items-using-for-loops

3

For JavaScript prototype functions that return a number, such as indexOf(), returning -1 just means that indexOf() couldn’t find the value used. In the case of the code you’ve shared, the function is indexOf(elem), and elem equals 3 in the call you’ve used, so all a -1 would mean is that the item in arr[i] doesn’t have a 3 in it.

Hope this helps!

4

I think that makes sense. Thanks for the help.

Would there be another way to change the ‘== -1’ into something else?

Just wondering. Thanks.

5

I don’t think there’s a way to do that without editing the prototype, which isn’t recommended.

6

if you are not interested in the index in case the element is present you can use includes, this method returns true/false