Steamroller, my solution is similar to provided, why doesn't it work?

JavaScript
1

Tell us what’s happening:
This is one of three questions I’m having trouble with. Basically, I think my solution works. I looked at the provided solution, Which works basically the same way, although uses push instead of concat as it’s array builder, but mine isn’t working.

I wouldnt post, but on an earlier challenge, where I was supposed to return undefined, I wasn’t able to do so by allowing the function to finish with no return, OR by returning the word “undefined” or undefined. and for that challenge I was 100% confident that my solution did meet requirements, if in other testing engines.

basically I don’t want to walk away thinking my solution has a problem if it actually works. I want to be confident that although there are other answers, mine DID function appropriately.

Your code so far


function steamrollArray(arr) {
  let result = [];
  let roll = function (item) {
    let rolled = [];
    if (Array.isArray(item)) {
      for (let i = 0; i < item.length; i++) {
        rolled.concat(roll(item[i]));
      }
      return rolled;
    } else {  
      return item;
    }
  }
  for (let i = 0; i < arr.length; i++) {
    result.concat(roll(arr[i]));
  }
  // I'm a steamroller, baby
  return result;
}

console.log(steamrollArray([1, [2], [3, [[4]]]]));

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/75.0.3770.100 Safari/537.36.

Link to the challenge:
https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/intermediate-algorithm-scripting/steamroller

2

concat creates/returns a new array instead of mutating the original array. You will need to assign the returned value a variable and then return it. You could assign the result back to rolled and result (after their respective for loops).

3

thanks! let me look at that. that’s probably it.

4

that worked. I’m going to go back and post the other question.