Review of the constructor function

What is a constructor function?

Constructors are used to assign values to initialized instantiated objects

Execution process

1. Create a new object by using the New keyword

2. The constructor assigns the newly created object to the This object within the function

3. Add members to new objects through the This keyword within a function

4. Return the newly created object by default

Precautions

1. Constructor name is best capitalized

2. Use with new

3. If you set the return value manually

A) return a basic type of data (including undefined and null), the function still returns the newly created object

b) Return an object of type data, the function will return this object

4. If you do not give constructor arguments when calling a function, the constructor will not create a new object, and this will point to the window, and the added attributes will be added to the window

What is a prototype?

When the constructor is created, the system creates a mysterious object associated with it by default, which is the prototype

The role of prototypes?

The properties and methods in the prototype can be shared by all objects instantiated by the constructor associated with it

Can expand built-in objects

How to get a prototype

constructor. prototype

Instantiates an object. __proto__

How prototypes are used

Direct Replacement prototypes

The prototype of the object created before replacing the prototype and the prototype of the object created after the substitution is not the same

Substitution is not a modification, it is a whole replacement.

Add members to the prototype using the object's dynamic properties (

(Member: A generic name for properties and methods)

. Cosntructor: The prototype function points to the constructor of the prototype

　A) When a point syntax is assigned to a property, the prototype is not searched.

b) when assigning a value using Point syntax , if the property does not exist in the object , it will be added to the object and will not be found in the prototype

Review of the constructor function