Help: "Iterate Through All an Array's Items Using For Loops"

JavaScript
#1

Tell us what’s happening:
Hi,

I’m getting stuck on this challenge and am just looking for some hints/feedback. To explain what I have so far…

  1. I have a nested For loop (“lion” & “tiger”) to loop through the content of the arrays.

  2. I then have an If statement that says if the elem DOES NOT exist in the array, push the array (using spread operator) to “newArr”

However it’s not working. I would really appreciate a hint to get me on the right track.

Thanks!

Your code so far


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

// change code here to test different cases:
console.log(filteredArray([10, 8, 3], [14, 6, 23], [3, 18, 6], 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

#2

Second loop is not needed. For example:
arr[0] = [10, 8, 3]
When you add second loop, you are looping through single numbers, for which .indexOf(elem) will not give you result that you expect.

1 Like
#3

Thanks for this, I made an update by removing the second loop, but still doesn’t seem to be working correctly. Another hint would be appreciated.

function filteredArray(arr, elem) {
  let newArr = [];
  // change code below this line
  for (let i=0; i < arr[i].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([10, 8, 3], [14, 6, 23], [3, 18, 6], 3));
#4

Are you sure about using arr[i].length here?

What do you think this line is doing?

1 Like
#5

Thank you, I updated the code to the below. One issue I was having is that I sometimes use codepen.io to demo the challenges.

With the below code I kept getting an “Uncaught TypeError: arr[i].indexOf is not a function at pen.js:-1” error message. But when I tested it on FCC, it passed. Do you know why there is a disconnect with codepen.io? This was causing me confusion.

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;
}
#6

The reason you are getting that error, is because you are not correctly calling the function. The test cases have a two-dimensional array as the first argument. Your code above has 4 arguments (the first 3 are one-dimensional arrays).

#7

Sure thing: https://codepen.io/alexnbuchanan/pen/GRgVpwx?editors=1111

Upon reviewing it, I know why, I had changed the array at the very bottom to test different iterations, there is a syntax error which is causing it to not work, my mistake!

#8