JavaScript this refers to the meaning of new and prototype, the prototype chain __this

In JavaScript, this is defined when created. What does this sentence mean?

function Foo () {

this.name = ' Peter ';

}

Foo ();

Console.log (name);//this is the global object when it is created, so the name here is Peter;

So what's different about adding a keyword new?

Let's say varobj = new Foo ();

In JavaScript, the new keyword does three things:

First, generate a new object

One, Varo = {}; Generate an Empty object o

Second, o.__proto__= foo.prototype;//the prototype chain to pass to O

Third, Foo.call (o);/to pass the value of oneself

return o;

When

New Foo ();

Console.log (name); The name is not defined

What is the inheritance of prototype? See Nanyi's article

var F = function () {};

F.prototype = Parent.prototype;

Child.prototype = new F ();

Child.prototype.constructor = child;

Because the object is passed by reference, when I assign a value f.prototype= parent.prototype, then f.prototype.xx= ' sth '; This time the original Parent.prototype will be changed accordingly, so to use the empty object as an intermediary.

Plus our definition of new, we can get:

var F = function () {};

F.prototype = Parent.prototype;

var o = {};

o.__proto__ = F.prototype;

F.call (o);

Child.prototype = O;

Child.prototype.constructor = child;

Since we assign an object to Child.prototype, when we change the constructor attribute to the child, we change only one property of the object o, not an O prototype. So it has no effect on the original parent.

Don't believe it.

Give it a try.

Console.log (O.prototype = = = o.__proto__); False

The prototype chain is to find its own attributes first, then find prototype, and then continue to look up.

var o = {};

var k = {

Call:function () {

Console.log (' a Try ');

}

};

K.__proto__.call = function () {

Console.log (' second try ');

};

o.__proto__ = k;

O.call ();