Javascript functional inheritance with prototypes

Question

In Douglas Crockford\'s JavaScript: The Good Parts he recommends that we use functional inheritance. Here\'s an example:

var mammal = function(spec, my         


        

Answer 1

if you want privacy and you dont like protyping you may or may-not like this approach:

(note.: it uses jQuery.extend)

var namespace = namespace || {};

// virtual base class
namespace.base = function (sub, undefined) {

    var base = { instance: this };

    base.hierarchy = [];

    base.fn = {

        // check to see if base is of a certain class (must be delegated)
        is: function (constr) {

            return (this.hierarchy[this.hierarchy.length - 1] === constr);
        },

        // check to see if base extends a certain class (must be delegated)
        inherits: function (constr) {

            for (var i = 0; i < this.hierarchy.length; i++) {

                if (this.hierarchy[i] == constr) return true;
            }
            return false;
        },

        // extend a base (must be delegated)
        extend: function (sub) {

            this.hierarchy.push(sub.instance.constructor);

            return $.extend(true, this, sub);
        },

        // delegate a function to a certain context
        delegate: function (context, fn) {

            return function () { return fn.apply(context, arguments); }
        },

        // delegate a collection of functions to a certain context
        delegates: function (context, obj) {

            var delegates = {};

            for (var fn in obj) {

                delegates[fn] = base.fn.delegate(context, obj[fn]);
            }

            return delegates;
        }
    };

    base.public = {
        is: base.fn.is,
        inherits: base.fn.inherits
    };

    // extend a sub-base
    base.extend = base.fn.delegate(base, base.fn.extend);

    return base.extend(sub);
};

namespace.MyClass = function (params) {

    var base = { instance: this };

    base.vars = {
        myVar: "sometext"
    }

    base.fn = {
        init: function () {

            base.vars.myVar = params.myVar;
        },

        alertMyVar: function() {

            alert(base.vars.myVar);
        }

    };

    base.public = {
        alertMyVar: base.fn.alertMyVar
    };

    base = namespace.base(base);

    base.fn.init();

    return base.fn.delegates(base,base.public);
};

newMyClass = new namespace.MyClass({myVar: 'some text to alert'});
newMyClass.alertMyVar();

the only downside is that because of the privacy scope you can only extend the virtual classes and not the instanceable classes.

here is an example of how i extend the namespace.base, to bind/unbind/fire custom events.

// virtual base class for controls
namespace.controls.base = function (sub) {

    var base = { instance: this };

    base.keys = {
        unknown: 0,
        backspace: 8,
        tab: 9,
        enter: 13,
        esc: 27,
        arrowUp: 38,
        arrowDown: 40,
        f5: 116
    }

    base.fn = {

        // bind/unbind custom events. (has to be called via delegate)
        listeners: {

            // bind custom event
            bind: function (type, fn) {

                if (fn != undefined) {

                    if (this.listeners[type] == undefined) {
                        throw (this.type + ': event type \'' + type + '\' is not supported');
                    }

                    this.listeners[type].push(fn);
                }

                return this;
            },

            // unbind custom event
            unbind: function (type) {

                if (this.listeners[type] == undefined) {
                    throw (this.type + ': event type \'' + type + '\' is not supported');
                }

                this.listeners[type] = [];

                return this;
            },

            // fire a custom event
            fire: function (type, e) {

                if (this.listeners[type] == undefined) {
                    throw (this.type + ': event type \'' + type + '\' does not exist');
                }

                for (var i = 0; i < this.listeners[type].length; i++) {

                    this.listeners[type][i](e);
                }

                if(e != undefined) e.stopPropagation();
            }
        }
    };

    base.public = {
        bind: base.fn.listeners.bind,
        unbind: base.fn.listeners.unbind
    };

    base = new namespace.base(base);

    base.fire = base.fn.delegate(base, base.fn.listeners.fire);

    return base.extend(sub);
};