Stack Data Structures, Functional, Functional Shared, Prototypal, Pseudoclassical Implementations

stackDataStructures.js

/**********FUNCTIONAL - SHARED STACK IMPLEMENTATION ****************/

var makeStack = function() {
    var stack = {
        storage: {},
        length: 0
    };

    extend(stack, stackMethods);
    return stack;
};

//extend methods to our stack object 
var extend = function(to, from) {
    for (var key in from) {
        to[key] = from[key];
    }
};

var stackMethods = {

    add: function(value) {
        this.storage[this.length] = value;
        this.length++;
    },

    remove: function() {
        if (this.size() > 0) {
            var result = this.storage[this.length - 1];
            delete this.storage[this.length - 1];
            this.length--;
            return result;
        } else {
            return null;
        }
    },
    
    size: function() {
        return this.length;
    }
};

//TESTS

var newStack = makeStack(); //create stack instance
newStack.add(10);
newStack.add('dogs');
console.log(newStack.storage); //{ '0': 10, '1': 'dogs' }
console.log(newStack.size()); //2
newStack.add(20); 
console.log(newStack.storage); //{ '0': 10, '1': 'dogs', '2': 20 }
newStack.remove();
console.log(newStack.storage); //{ '0': 10, '1': 'dogs' }
newStack.remove();
newStack.remove();
console.log(newStack.storage); // {}
console.log(newStack.remove()); // null


/*****************FUNCTIONAL - FUNCTIONAL IMPLEMENTATION****************************/

var makeStack = function() {
    //set local variables to use throughout
    var length = 0,
        storage = {},
        stack = {

            /*****METHODS*****/
            push: function(value) {
                storage[length] = value;
                length++;
            },

            pop: function() {
                if (length > 0) {
                    var result = storage[length - 1];
                    delete storage[length - 1];
                    length--;
                    return result;
                }
            },

            size: function() {
                return length;
            },

            storage: function() {
                return storage;
            }
        };
    return stack;

};
var stack = makeStack();
stack.push(10);
stack.push(20);
console.log(stack.size()); //2
console.log(stack.storage()); //{ '0': 10, '1': 20 }


/*****************FUNCTIONAL - PSEUDO-CLASSICAL IMPLEMENTATION****************************/

//create stack constructor
var Stack = function() {
    this.length = 0;
    this.storage = {};
};

//create an add/push method for our prototype 
Stack.prototype.add = function(value) {
    this.storage[this.length] = value;
    this.length++;
};

//create a remove/pop method for our prototype 
Stack.prototype.remove = function() {
    //make sure item exists to remove
    if (this.length > 0) {
        //get last item
        var result = this.storage[this.length - 1];
        delete this.storage[this.length - 1];
        this.length--;
        return result;
    }
};

//let us check the size
Stack.prototype.size = function() {
    return this.length;
};


//create a new instance of Stack using the new
//to instantiate our class
var newStack = new Stack();
newStack.add(10);
console.log(newStack);