Can someone explain a line of code in Basic Data Structures 11?

JavaScript
1

Tell us what’s happening:

Your code so far


function filteredArray(arr, elem) {
let newArr = [];
// Only change code below this line
for(let i = 0; i < arr.length; i++) {


//HERE is the line of code I am confused about. Can someone make a detailed explanation of each element in this statement? 

if (arr[i].indexOf(elem) === -1) {
  newArr.push(arr[i])
} 
}
// Only change code above this line
return newArr;
}

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:

2

if (arr[i].indexOf(elem) === -1)
checks if the element is in the inner array (arr[i])).
if the element is present it will return the index of elem if not it will return -1
so we are checking for elements that are not in array(-1) and pushing them into new array.

3

indexOf returns the first index at which the element is present in the array, if it isn’t it returns -1

so, arr[i] is the array being checked, elem is the element that could be in the array, and the === -1 is making so that if the element is not present (-1 === -1) everything evaluates to true and the if statement is executed

4

Thank you guys, it helped a lot!

5