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OLOO (objects linked to other objects) pattern explored (with comparison to the prototype style of the same code)
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function Foo(who) { | |
this.me = who; | |
} | |
Foo.prototype.identify = function() { | |
return "I am " + this.me; | |
}; | |
function Bar(who) { | |
Foo.call(this,"Bar:" + who); | |
} | |
Bar.prototype = Object.create(Foo.prototype); | |
Bar.prototype.constructor = Bar; // "fixes" the delegated `constructor` reference | |
Bar.prototype.speak = function() { | |
alert("Hello, " + this.identify() + "."); | |
}; | |
var b1 = new Bar("b1"); | |
var b2 = new Bar("b2"); | |
b1.speak(); // alerts: "Hello, I am Bar:b1." | |
b2.speak(); // alerts: "Hello, I am Bar:b2." | |
// some type introspection | |
b1 instanceof Bar; // true | |
b2 instanceof Bar; // true | |
b1 instanceof Foo; // true | |
b2 instanceof Foo; // true | |
Bar.prototype instanceof Foo; // true | |
Bar.prototype.isPrototypeOf(b1); // true | |
Bar.prototype.isPrototypeOf(b2); // true | |
Foo.prototype.isPrototypeOf(b1); // true | |
Foo.prototype.isPrototypeOf(b2); // true | |
Foo.prototype.isPrototypeOf(Bar.prototype); // true | |
Object.getPrototypeOf(b1) === Bar.prototype; // true | |
Object.getPrototypeOf(b2) === Bar.prototype; // true | |
Object.getPrototypeOf(Bar.prototype) === Foo.prototype; // true |
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var Foo = { | |
Foo: function(who) { | |
this.me = who; | |
return this; | |
}, | |
identify: function() { | |
return "I am " + this.me; | |
} | |
}; | |
var Bar = Object.create(Foo); | |
Bar.Bar = function(who) { | |
// "constructors" (aka "initializers") are now in the `[[Prototype]]` chain, | |
// so `this.Foo(..)` works easily w/o any problems of relative-polymorphism | |
// or .call(this,..) awkwardness of the implicit "mixin" pattern | |
this.Foo("Bar:" + who); | |
return this; | |
}; | |
Bar.speak = function() { | |
alert("Hello, " + this.identify() + "."); | |
}; | |
var b1 = Object.create(Bar).Bar("b1"); | |
var b2 = Object.create(Bar).Bar("b2"); | |
b1.speak(); // alerts: "Hello, I am Bar:b1." | |
b2.speak(); // alerts: "Hello, I am Bar:b2." | |
// some type introspection | |
Bar.isPrototypeOf(b1); // true | |
Bar.isPrototypeOf(b2); // true | |
Foo.isPrototypeOf(b1); // true | |
Foo.isPrototypeOf(b2); // true | |
Foo.isPrototypeOf(Bar); // true | |
Object.getPrototypeOf(b1) === Bar; // true | |
Object.getPrototypeOf(b2) === Bar; // true | |
Object.getPrototypeOf(Bar) === Foo; // true |
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