├── Proto.js
└── README


/Proto.js:
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 1 | ////////// API //////////
 2 | 
 3 | // To be part of ECMAScript.next
 4 | if (!Object.getOwnPropertyDescriptors) {
 5 |     Object.getOwnPropertyDescriptors = function (obj) {
 6 |         var descs = {};
 7 |         Object.getOwnPropertyNames(obj).forEach(function(propName) {
 8 |             descs[propName] = Object.getOwnPropertyDescriptor(obj, propName);
 9 |         });
10 |         return descs;
11 |     };
12 | }
13 | 
14 | /**
15 |  * The root of all classes that adhere to "the prototypes as classes" protocol.
16 |  * The neat thing is that the class methods "new" and "extend" are automatically
17 |  * inherited by subclasses of this class (because Proto is in their prototype chain).
18 |  */
19 | var Proto = {
20 |     /**
21 |      * Class method: create a new instance and let instance method constructor() initialize it.
22 |      * "this" is the prototype of the new instance.
23 |      */
24 |     new: function () {
25 |         var instance = Object.create(this);
26 |         if (instance.constructor) {
27 |             instance.constructor.apply(instance, arguments);
28 |         }
29 |         return instance;
30 |     },
31 | 
32 |     /**
33 |      * Class method: subclass "this" (a prototype object used as a class)
34 |      */
35 |     extend: function (subProps) {
36 |         // We cannot set the prototype of "subProps"
37 |         // => copy its contents to a new object that has the right prototype
38 |         var subProto = Object.create(this, Object.getOwnPropertyDescriptors(subProps));
39 |         subProto.super = this; // for super-calls
40 |         return subProto;
41 |     },
42 | };
43 | 
44 | /**
45 |  * Optional: compatibility with constructor functions
46 |  */
47 | Function.prototype.extend = function(subProps) {
48 |     var constrFunc = this;
49 |     // Let a prototype-as-class extend a constructor function constrFunc.
50 |     // Step 1: tmpClass is Proto, but as a sub-prototype of constrFunc.prototype
51 |     var tmpClass = Proto.extend.call(constrFunc.prototype, Proto);
52 |     // Step 2: tmpClass is a prototype-as-class => use as such
53 |     return tmpClass.extend(subProps);
54 | };
55 | 
56 | ////////// Demo //////////
57 | 
58 | //***** Code *****
59 | // Superclass
60 | var Person = Proto.extend({
61 |     constructor: function (name) {
62 |         this.name = name;
63 |     },
64 |     describe: function() {
65 |         return "Person called "+this.name;
66 |     },
67 | });
68 | 
69 | // Subclass
70 | var Employee = Person.extend({
71 |     constructor: function (name, title) {
72 |         Employee.super.constructor.call(this, name);
73 |         this.title = title;
74 |     },
75 |     describe: function () {
76 |         return Employee.super.describe.call(this)+" ("+this.title+")";
77 |     },
78 | });
79 | //*/
80 | 
81 | /***** Interaction *****
82 | var jane = Employee.new("Jane", "CTO"); // normally: new Employee(...)
83 | > Employee.isPrototypeOf(jane) // normally: jane instanceof Employee
84 | true
85 | > jane.describe()
86 | 'Person called Jane (CTO)'
87 | */
88 | 


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/README:
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 1 | Proto.js – prototypes as classes
 2 | 
 3 | The core idea of Proto.js is that many things become simpler in JavaScript if you make the prototype the class and not the constructor.
 4 | Details: http://www.2ality.com/2011/06/prototypes-as-classes.html
 5 | 
 6 | Code:
 7 | 
 8 |     // Superclass
 9 |     var Person = Proto.extend({
10 |         constructor: function (name) {
11 |             this.name = name;
12 |         },
13 |         describe: function() {
14 |             return "Person called "+this.name;
15 |         }
16 |     });
17 | 
18 |     // Subclass
19 |     var Employee = Person.extend({
20 |         constructor: function (name, title) {
21 |             Employee.super.constructor.call(this, name);
22 |             this.title = title;
23 |         },
24 |         describe: function () {
25 |             return Employee.super.describe.call(this)+" ("+this.title+")";
26 |         }
27 |     });
28 | 
29 | Interaction:
30 | 
31 |     var jane = Employee.new("Jane", "CTO"); // normally: new Employee(...)
32 | 
33 |     > Employee.isPrototypeOf(jane) // normally: jane instanceof Employee
34 |     true
35 | 
36 |     > jane.describe()
37 |     'Person called Jane (CTO)'
38 | 


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