01. stack.js

/* Stacks! */

// functions: push, pop, peek, length

let letters = []; // this is our stack

let word = "freeCodeCamp"

let rword = "";

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

// pop off the stack in reverse order
for (let 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.");
}



// Creates a stack
let 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--;
        let result = this.storage[this.count];
        delete this.storage[this.count];
        return result;
    }
    
    this.size = function() {
        return this.count;
    }
    
    // Returns the value at the end of the stack
    this.peek = function() {
        return this.storage[this.count-1];
    }
}

let myStack = new Stack();

myStack.push(1);
myStack.push(2);
console.log(myStack.peek());
console.log(myStack.pop());
console.log(myStack.peek());
myStack.push("freeCodeCamp");
console.log(myStack.size());
console.log(myStack.peek());
console.log(myStack.pop());
console.log(myStack.peek());

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