extendable-base/lib/extendable.js

Simple library for setting up Javascript classes based on Backbone.extend

var _ = require('underscore');

/**
 * Simple base class that pulls in the extend syntax from Backbone.
 */
var Extendable = function() { };

// (Copy of Backbone.extend)
// Set up the prototype chain, for subclasses.
// Similar to `goog.inherits`, but uses a hash of prototype properties and
// class properties to be extended.
Extendable.extend = function(protoProps, staticProps) {
    var parent = this;
    var child;

    // The constructor function for the new subclass is either defined by you
    // (the "constructor" property in your `extend` definition), or defaulted
    // by us to simply call the parent's constructor.
    if (protoProps && _.has(protoProps, 'constructor')) {
        child = protoProps.constructor;
    } else {
        child = function() { return parent.apply(this, arguments); };
    }

    // Add static properties to the constructor function, if supplied.
    _.extend(child, parent, staticProps);

    // Set the prototype chain to inherit from `parent`, without calling
    // `parent`'s constructor function.
    var Surrogate = function() { this.constructor = child; };
    Surrogate.prototype = parent.prototype;
    child.prototype = new Surrogate();

    // Add prototype properties (instance properties) to the subclass,
    // if supplied.
    if (protoProps) { _.extend(child.prototype, protoProps); }

    // Set a convenience property in case the parent's prototype is needed
    // later.
    child.__super__ = parent.prototype;

    return child;
};

// Set up inheritance with a specific parent class.
Extendable.inherits = function(parent, protoProps, staticProps) {
    var child = Extendable.extend.call(parent, protoProps, staticProps);
    child.extend = Extendable.extend;
    return child;
};

module.exports = Extendable;