Determine the Big-O complexity:

Even or odd: constant time complexity 0(1)
  function isEven(value){
    if (value % 2 == 0){
      return true;
    }
    else
      return false;
  }
  // No matter the size of your input, the algorithm will take the same amount of time to complete.
  // Examples of constant time complexity are: Adding, dividing, accessing an array item.

Are you here?: Polynomial 0(n^k)
  function areYouHere(arr1, arr2) {
    for (let i=0; i<arr1.length; i++) {
        const el1 = arr1[i];
        for (let j=0; j<arr2.length; j++) {
            const el2 = arr2[j];
            if (el1 === el2) return true;
        }
    }
    return false;
  }
  // The easiest way to understand polynomial time complexity is with nested loops.
  // An algorithm that requires two levels of looping over an input would be O(n^2).

Doubler: linear run time complexity 0(n)
  function doubleArrayValues(array) {
    for (let i=0; i<array.length; i++) {
        array[i] *= 2;
    }
    return array;
  }
  //