Add Items to an Array with push() and unshift() -- explanation

Tell us what’s happening:

I was wondering why in this section are things repeated from the basic javascript section? I’m not complaining, just wondering about the reasoning behind it.

Your code so far


function mixedNumbers(arr) {
  // change code below this line

  // change code above this line
  return arr;
}

// do not change code below this line
console.log(mixedNumbers(['IV', 5, 'six']));

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.99 Safari/537.36.

Link to the challenge:
https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/basic-data-structures/add-items-to-an-array-with-push-and-unshift