Extends in javascript

Question

Can someone please help me understand this code? Seems too convoluted to me.

var __extends = this.__extends || function (d, b) {
    function __() { this.constructor = d; }
    __.prototype = b.prototype;
    d.prototype = new __();
};


var PageView = (function (_super) {
    "use strict";

    __extends(MyPageView, _super);

 function MyPageView(rootElement, viewModelParameter, calendarWeeksViewModel) {
});


}

Answer 1

So basically

__extends(MyPageView, _super);

Think in terms ofinheritance in a Object Oriented language. Where a class is extending a Super class or a base class..

So basically here MyPageView will extend the functionality and implementation of the super class .

So lets say the base View has method A() and method B() and the current View has method C(), then you current view has access to all the three methods A() , B() and C() in it's view.

But lets say MyPageView has method B() , defined in it , then the method inside the view will take precedence over the Method B() of Super View

var __extends = this.__extends || function (d, b) {
    function __() { this.constructor = d; }
    __.prototype = b.prototype;
    d.prototype = new __();
};

Every function has a magical prototype property.

 var __extends = this.__extends || function (d, b) {

Cheks if that function is available in that context , if not define a function , that takes 2 arguments , The object that is to be extended and the object from which it is extended..

function __() { this.constructor = d; }

Defining a new function called __ in which that constructor property of the context is bound to object d

 __.prototype = b.prototype;

The prototype property of the Object __ is pointed to the b.prototype chain..

 d.prototype = new __();

The accessing of methods of Super View happens here , where you are setting the prototype property of the Object here..

So when the new instance is created, if the method is not available , then because of the prototype on the object , it will check the methods in the Super view because it is available on the function __ which is tied to object d