This in js points to the prototype object

The JavaScript parser will pass an implicit parameter inside the function every time the function is called. This implicit parameter is this, which points to an object.We call this object the context object of the function execution.Depending on how the function is called, this will point to a different object.

1. When called in the form of a function, this is always window.

2. When called in the form of a method, this is the object that calls the method.

prototype

For each function we create, the parser will add a property prototype to the function, which corresponds to an object, which is what we call a prototype object.

If the function is used as a normal function to call the prototype without any effect, when the function is called in the form of a constructor, the object it creates will have an implicit property, pointing to the prototype object of the constructor, we can pass

span style="color:#ff9900;">__proto__ to access this property.As shown below:

The prototype object is equivalent to a public area. All instances of the same class can access this prototype object. We can uniformly set the common content of the object to the prototype object.

Add property a to the prototype of MyClassSyntax: MyClass.prototype.a=123;

When we access a property or method of an object, it will be found in the object itself, if there is one, it will be used directly, if not, it will be found in the prototype object, and if it is found, it will be used directly.As shown below:

When we create a constructor, we can add the common properties and methods of these objects to the prototype of the constructor, so that we do not need to add each object separately, and it will not affect the global scope.Every object has these properties and methods.

The prototype object of the prototype object...

The prototype object is also an object, so it also has a prototype. When we use the properties or methods of an object, we will find it in itself. If there is one in itself, we will use it directly. If not, we will go to the prototype object to find it. If the prototypeobject, use it.If not then go to the prototype of the prototype to find.Find a as shown below.

The prototype of the object object has no prototype. If it is still not found in the object, undefined is returned.