Javascript Inheritance and Object Literal

Question

In JavaScript, it is said that object literals have prototype linking, but function objects have both prototype linking and a prototype property.

So, based on the above, can one say that inheritance (which uses the prototype property), is possible only with function objects (constructor version) and not with object literals?

Also, to add, the __proto__ property is not accessible in all the browsers...

Answer 1

Short version:

Yes: The prototype chain cannot be set up or modified by assigning to an object's prototype property. You cannot set up inheritance by creating an object with an object literal and then giving it a property called prototype. Such property will be called prototype, but will not be considered for prototypal inheritance.

Longer:

If you access a property that is undefined, that object's inheritance chain is checked. So, if obj['prop'] is undefined, then obj.prototype['prop'] will be checked. In many browsers, the prototype property is implemented internally as the __proto__ property, but that is besides the point. Rather, the point is that if some property is undefined, the object's prototype is checked for that property.

As people have said in comments, it's only possible to bestow an object with a prototype that provides the above-described inheritance by assigning that object to a function's prototype property and then using that function as a constructor.

But, the prototype property of an object produced by constructor invokation is not object.hasOwnProperty('prototype'). On the other hand, if you assign a prototype property to an object, then that object will object.hasOwnProperty('prototype'), but then object.prototype will have nothing to do with the prototype chain—it'll just be a regular property, and will be happened to call prototype.

To demonstrate this:

var foo = {};
foo.prototype = {bar: 'hello'};
console.log(foo.bar); // undefined
console.log(foo.prototype); // Object {bar: "hello"}
console.log(foo.hasOwnProperty('prototype')); // true

var Foo = function() {};
Foo.prototype = {bar: 'hello'};
var f = new Foo;
console.log(f.bar); // 'hello';
console.log(f.hasOwnProperty('bar')); // false
console.log(f.prototype); // undefined
console.log(f.hasOwnProperty('prototype')); // false