Web Front-end
JS Tutorial
JavaScript Tutorial: Incomplete Inheritance (JS Prototype Chain)_Basic Knowledge
JavaScript Tutorial: Incomplete Inheritance (JS Prototype Chain)_Basic Knowledge
Javascript inheritance is very different from standard oop inheritance. Javascript inheritance uses prototype chain technology. Each class will put "member variables" and "member functions" on the prototype. Js all use superclass Link it up, i.e. C.prototype.superclass = C.superclass = P.prototype;
When var c = new C(), c.__proto__ = C.prototype;
When c accesses "member variable ", if __proto__ cannot be obtained, it will search in C.prototype. If it does not exist, it will search in the prototype of the parent class, because only __proto__ is allocated when the object is created (each object is allocated independently ), others are allocated when defining (shared by each object). At this time, if the "member variable" in C.prototype is accessed as an object, the "member variable" itself will not be modified, but the "member variable" object will be modified. When modifying the members of the "member variable" object, the members of the modified "member variable" object will be shared by all object instances, which violates the original intention of the class design.
For example:
'package'.j(function () {
'class A'.j(function () {
jpublic({
v:{a: 1}
});
jprivate({
p:{a:1}
);
});
'class B extends A'.j(function () {
});
});var b1 = new B();
b1.v.a = 5;
b1.x.a = 5;
console.log(b1.v.a) // The output is 5
console.log(b1.x.a) // The output is 5
console.log(b2.x.a) // The output is 1
console.log(b2.p.a) // If not available, it will prompt that p does not exist
How to solve this problem?
A. The member "member variable" (itself an object) like v is not defined on the prototype chain, but is called in the constructor. At this time, when the object instance is created, it will be in the object's __proto__ Distributed on.
B. Only read-only "member variables" (which themselves are objects) are defined on the prototype chain
The members in the "member variables" (which themselves are objects) defined by C.jpublic are only read-only members. Remember not to assign values, otherwise they will be shared among various instances.
Hot AI Tools
Undresser.AI Undress
AI-powered app for creating realistic nude photos
AI Clothes Remover
Online AI tool for removing clothes from photos.
Undress AI Tool
Undress images for free
Clothoff.io
AI clothes remover
Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!
Hot Article
Hot Tools
Notepad++7.3.1
Easy-to-use and free code editor
SublimeText3 Chinese version
Chinese version, very easy to use
Zend Studio 13.0.1
Powerful PHP integrated development environment
Dreamweaver CS6
Visual web development tools
SublimeText3 Mac version
God-level code editing software (SublimeText3)
Hot Topics
What should I do if I encounter garbled code printing for front-end thermal paper receipts?
Apr 04, 2025 pm 02:42 PM
Frequently Asked Questions and Solutions for Front-end Thermal Paper Ticket Printing In Front-end Development, Ticket Printing is a common requirement. However, many developers are implementing...
Demystifying JavaScript: What It Does and Why It Matters
Apr 09, 2025 am 12:07 AM
JavaScript is the cornerstone of modern web development, and its main functions include event-driven programming, dynamic content generation and asynchronous programming. 1) Event-driven programming allows web pages to change dynamically according to user operations. 2) Dynamic content generation allows page content to be adjusted according to conditions. 3) Asynchronous programming ensures that the user interface is not blocked. JavaScript is widely used in web interaction, single-page application and server-side development, greatly improving the flexibility of user experience and cross-platform development.
Who gets paid more Python or JavaScript?
Apr 04, 2025 am 12:09 AM
There is no absolute salary for Python and JavaScript developers, depending on skills and industry needs. 1. Python may be paid more in data science and machine learning. 2. JavaScript has great demand in front-end and full-stack development, and its salary is also considerable. 3. Influencing factors include experience, geographical location, company size and specific skills.
How to merge array elements with the same ID into one object using JavaScript?
Apr 04, 2025 pm 05:09 PM
How to merge array elements with the same ID into one object in JavaScript? When processing data, we often encounter the need to have the same ID...
Is JavaScript hard to learn?
Apr 03, 2025 am 12:20 AM
Learning JavaScript is not difficult, but it is challenging. 1) Understand basic concepts such as variables, data types, functions, etc. 2) Master asynchronous programming and implement it through event loops. 3) Use DOM operations and Promise to handle asynchronous requests. 4) Avoid common mistakes and use debugging techniques. 5) Optimize performance and follow best practices.
How to achieve parallax scrolling and element animation effects, like Shiseido's official website?
or:
How can we achieve the animation effect accompanied by page scrolling like Shiseido's official website?
Apr 04, 2025 pm 05:36 PM
Discussion on the realization of parallax scrolling and element animation effects in this article will explore how to achieve similar to Shiseido official website (https://www.shiseido.co.jp/sb/wonderland/)...
The difference in console.log output result: Why are the two calls different?
Apr 04, 2025 pm 05:12 PM
In-depth discussion of the root causes of the difference in console.log output. This article will analyze the differences in the output results of console.log function in a piece of code and explain the reasons behind it. �...
How to implement panel drag and drop adjustment function similar to VSCode in front-end development?
Apr 04, 2025 pm 02:06 PM
Explore the implementation of panel drag and drop adjustment function similar to VSCode in the front-end. In front-end development, how to implement VSCode similar to VSCode...
