shift() & unshift() let you do stuff to arrays starting at the beginning.
Here is a little more detail:
shift(): Removes an item from the beginning of an array and returns the array item that was removed.unshift(): Adds items to the beginning of an array and returns the new length of the array.
let myArray = [1,2,3];
console.log(myArray.shift()); // 1
console.log(myArray); // [2, 3]
myArray = [1,2,3];
console.log(myArray.unshift(-2, -1, 0)); // 6
console.log(myArray); // [-2, -1, 0, 1, 2, 3]