Reference for some example methods and properties inherited in JavaScript

Reference for some example methods and properties inherited in JavaScript_javascript skills

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Release： 2016-05-16 18:21:42

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The role of the prototype attribute:
Use the prototype attribute to provide a set of basic functions of the object's class. New instances of an object "inherit" the operations assigned to the object's prototype.

Function of the prototype attribute:
All JavaScript internal objects have a read-only prototype attribute. Functionality can be added to the prototype of an internal object, but the object cannot be given a different prototype.
However, user-defined objects can be assigned to new prototypes.

The role of the constructor attribute:
constructor represents a function that creates an object.

Function of the constructor property:
The constructor property is a member of all objects with prototype. They include all JavaScript internal objects except Global and Math objects.
The constructor attribute holds a reference to a function that constructs a specific object instance.

A Use prototype to add attributes of objects [Method 1]
Example:

Copy code The code is as follows :

B Use prototype to add attributes of objects [Method 2]
Example:

Copy code The code is as follows:

C uses prototype to inherit the prototype attributes of the parent class
Example:

Copy the code The code is as follows:

 
<script> <br>function Person(_name){ <br>this.name = _name; <br>} <br>//Create object (used to change prototype prototype object) <br>function addSex(_sex){ <br>this.sex = _sex; <br>} <br>//Change the prototype object <br>Person.prototype = new addSex('male'); <br>var p = new Person( 'xugang'); <br>alert("The prototype of p is: " p.constructor); <br>//Print all attributes<br>for(var i in p){ <br>//alert(p[ i]); <br>} <br><br>// ================= Inheritance================ = <br>//Create the sub-object Student <br>function Student(_study){ <br>this.study = _study; <br>} <br>// Let Student inherit Person through prototype <br>Student.prototype = new Person('Andy Lau'); <br>var stu1 = new Student('JS'); <br>alert("The prototype of stu1 is: " stu1.constructor); <br>for(var i in stu1){ <br>alert(stu1[i]); <br>} <br></script> 

Because the prototype of the Student object is changed to the Person object, and the prototype of the Person object is changed to addSex , so the prototype of the Student object is addSex.
Note: The prototype of an object is determined at the moment of new object. If it is changed after new object, it will be invalid!

D How to set the prototype object and constructor of an object
Example:

Copy code The code is as follows:

The results are as follows:
b's construction method: B method
b's prototype object's construction method: C method
Attribute: age value: 42
Attribute: name Value: Andy Lau

The __proto__ variable used to save the prototype in the E object
Example:

Copy the code The code is as follows:

The result in Firefox is as follows:
[object Object]
Super_Person method
Super_Person method