JavaScript Factory Inheritance

factory-inheritance.js

(function() {
'use strict';

// Create a factory function (a function that returns an object).
function aFactory() {
    // Create a data store.
    var _data = [];
    
    // Add supplied arguments to the data store.
    if (arguments.length)
        _data.push.apply(_data, arguments);
        
    return {
        // Store a reference to the factory that created this object.
        factory: aFactory,
        
        // Create a method to add items to the data store.
        add: function add() {
            _data.push.apply(_data, arguments);  
        },
        
        // Create a method to iterate the data store.
        each: function each(action, context) {
            _data.forEach(action, context);
        },
        
        // Create a method to return a copy of this object.
        copy: function copy() {
            return this.factory.apply(null, _data);    
        },
        
        // Create a method to clear the data.
        clear: function clear() {
            _data = [];    
        },
        
        // Create a method to return a copy of the data object.
        data: function data() {
            return _data.slice(0, _data.length);
        }
    };
}

// Create a new factory function that will inherit from aFactory.
function myFactory() {
    // Create a reference to the original factory.
    var _super = aFactory.apply(null, arguments);
    
    // Create a new object with the original factory as its prototype.
    var self = Object.create(_super);
    
    // Set the factory property of the new object.
    self.factory = myFactory;
    
    // Optionally provide a reference to the original factory.
    self._super = _super;
    
    // Add a new method to the new object.
    self.toString = function toString() {
        return this.data().join(',');  
    };
    
    // Return the new object.
    return self;
}

console.log('Create a factory with some starter data')
var f = myFactory(1, 2, 3);
console.log('Data:', f.data());
console.log('Add some items (4, 5, 6)');
f.add(4, 5, 6);
console.log('New data:', f.data());
console.log('Iterate the data store');
f.each(function(item) {
    console.log('  item', item); 
});
console.log('Factory method:', f.factory);
console.log('Super\'s factory method:', f._super.factory);
console.log('Output from toString:', '' + f);
console.log('Copy myFactory');
var nf = f.copy();
console.log('The copy\'s factory method:', nf.factory);
})();