OO – Exercise Solution (Bonus B)

JavaScript

/**
 * OO – Exercise
 * 
 * 1. Collection object
 *   a. It should have a "add" method, which accepts an Item instance
 *   b. It should have a "remove" method, which removes the provided Item
 *   c. It should have a "size" method, which returns the size of internal data
 *   d. It should have a "contains" method, which returns a boolean indicating 
 *      whether the Item exists in internal data
 * 2. Item object
 *   a. It should have a "get" method that accepts a property name
 *   b. It should have a "set" method that accepts a property name and value
 * 3. General
 *   a. We should be able to create multiple instances of Item and store them
 *      in one or more instances of Collection
 *   b. Each instance should be distinct and independent from other instances
 *      of the same type
 * 5. BONUS
 *   a. Create a property on Item called "stores", that is an instance of 
 *      Collection.  When an Item is added to or removed from a Collection, 
 *      it will update this property with the Collection instance
 *   b. Make all data accessible only through exposed methods
 *   c. If you are feeling particularly ambitious, abstract any common logic
 *      to a parent object, and inherit from it
 */
function Collection(id) {

    var data = [];

    this.id = id;

    this.add = function (itemToAdd) {
        if (!_.contains(data, itemToAdd))
            data.push(itemToAdd);
    };

    this.contains = function (item) {
        return _.contains(data, item);
    };

    this.each = function (fn) {
        data.forEach(fn);
    };

    this.filter = function (fn) {
        return data.filter(fn);
    };

    this.remove = function (itemToRemove) {

        if (this.contains(itemToRemove)) {

            data = data.filter(function (item) {
                return item !== itemToRemove;
            });

        }

    };

    this.size = function () {
        return data.length;
    };

}

function Item(id) {

    var data = new Collection(id + 'Data');

  ...