3.js

function createArrayOfFunctions(y) {
    var arr = [];
    // fix:  for (let i = 0; i < y; i++) {
    for (var i = 0; i < y; i++) {
        arr[i] = function (x) {
            return x + i;
        }
         // if we run arr[i] immediately inside the loop, we get the desired function.     
    }
    // The problem is that the i inside each generated function all increment with each iteration. (scope leaking)          
    // so all of the functions here (outside the loop) have the same value of i (the last value)
    // instead of each digit between 0 and the input number
    return arr;
}

// to fix we can either put the arr variable outside the function and make it global, or a more modern way is
// is to make change var in the for loop into let. this works as let creates a new version of i each loop