// for loop
let coll = [1, 2, 3];

for (let i = 0; i < coll.length; i++) {
    coll[i] = coll[i] + 1;
}

// map
let coll2 = [1, 2, 3];

// notice I set what map returns to a variable
// map returns a new array
let newColl = coll2.map(num => num + 1);

//coll and newColl are the same thing now