Some income statement in advance, prototyping, static methods

A statement in advance:

There are three statement ahead of the process: create, initialize, assign:

the console.log (X);     // undefined 
function XXX () {};
 var X = 10 ; 

// equivalent 
var X = undefined;     // create and initialize 
function XXX () {}; 
X = 10;     // Assignment

 

But let not only create assignments:

the console.log (X);     // given 
the let X = 10 ;
 function XXX () {}; 

// equivalent to 
the let X;
 function XXX () {};

 

Second, prototype

Usually we will create an object like this:

var Plane=function(){
    this.name='plane';
}

var plane=new Plane();
plane.name='plane1';

Apart outer example by a new, can also be cloned by:

var plane2=Object.create(plane);

Each object we encounter in JavaScript, actually comes from Object.prototype clone objects, Object.prototype is their prototype. To create an object with the new operator process, in fact, only the object to clone Object.prototype, then some other additional operation process.

JavaScript to object provides __proto__, __proto__ default attribute of an object will point to the prototype object to its constructor:

function Animal(name){
     this.name=name;
}

var dog=new Animal();
console.log(dog.__proto__===Animal.prototype);    // true

 

Third, the static method

Din Tai defined by static methods, static methods can be called directly:

Animal {class 
    spaeak () { 
        return  the this ; 
    } 
    static EAT () { 
        return  the this ; 
    } 
} 

Animal.speak ();     // error 
Animal.eat ();     // Direct call