javascript stack and queue

stack-and-queue-in-javascript.js

//-- stack -----------
let stackArr = [];
stackArr.push(2);       //  [2] 
stackArr.push(5);       //  [2, 5]

let item = stackArr.pop(); // stackArr is now [2] //
console.log(item);      // displays 5

//-- queue -----------
let queueArr = [];
queueArr.push(2);         //  [2]
queueArr.push(5);         //  [2, 5]
let itemB = queueArr.shift(); // queueArr is now [5]
console.log(itemB);              // displays 2

/*
  push: add one (or more) element to end of array
  pop: remove from end of array
  shift: remove first element from array
  unshift: adds one (or more) element to the beginning of an array.
  
  BUT NOTE:
  using Array.shift() / .unshift() on a large array is not efficient, as other elements have to re-adjust position.
  */