stacks.js

// Stacks

// functions: push, pop, peek, length

var letters = [] // this is our stack
var word = "racecar"
var rword = "";

// put letters of word into stack
for (var i = 0; i < word.length; i++) {
  letters.push(word[i])
}

// pop off the stack in reverse order
for (var i = 0; i < word.length; i++) {
  rword += letters.pop();
}

if (rword === word) {
  console.log(word + " is a palindrome.")
}
else {
  console.log(word + " is not a palindrome.")
}

// ==============================================

const Stack = function () {
  this.count = 0
  this.storage = {}

  // Adds a value onto the end of the stack
  this.push = function(value) {
    this.storage[this.count] = value;
    this.count++;
  }

  // Removes and returns the value at the end of the stack
  this.pop = function() {
    if (this.count === 0) {
      return undefined
    }
    this.count--
    const result = this.storage[this.count]
    delete this.storage[this.count]
    return result
  }

  this.size = function () {
    return this.count
  }

  this.peek = function() {
    return this.storage[this.count - 1]
  }
}

const myStack = new Stack()
myStack.push(1)
myStack.push(2)
console.log(myStack.peek())
console.log(myStack.pop())
console.log(myStack.peek())
myStack.push("TESTING")
console.log(myStack.size())
console.log(myStack.peek())
console.log(myStack.pop())
console.log(myStack.peek())