Detailed explanation of JS prototype
This article mainly shares with you the detailed explanation of JS prototype and the 5 rules of prototype. I hope this article can help everyone.
All reference types (arrays, objects, functions) have object characteristics, which can be freely extended attributes (except "null")
var obj ={};obj.a=100//100var arr=[];arr.a=100//100function fn(){}
fn.a=100//100All application types have a proto attribute (implicit prototype), and the attribute value is an ordinary object
console.log(obj.__proto__);//{constructor: ƒ, __defineGetter__: ƒ, __defineSetter__: ƒ, hasOwnProperty: ƒ, __lookupGetter__: ƒ, …}console.log(arr.__proto__);//[constructor: ƒ, concat: ƒ, pop: ƒ, push: ƒ, shift: ƒ, …]console.log(fn.__proto__);
//ƒ () { [native code] }All functions have a prototype attribute (explicit prototype), and the attribute value is also an ordinary object
console.log(fn.prototype)
//{constructor: ƒ}All reference types The proto attribute value points to its constructor prototype attribute value (that is, the implicit prototype of all reference types points to the explicit prototype of his constructor)
console.log(obj.__proto__===Object.prototype); //true//Object是一个构造函数
When trying to get a certain attribute of an object, if the object itself does not have this attribute, then it will look for it in its proto (that is, the prototype of its constructor)
/*测试*/function Foo(name,age){
this.name = name;
}
Foo.prototype.alertName = function(){//由于Foo.prototype本身也是一个对象，而对象是可以自由扩展属性的
alert(this.name);
}var f = new Foo('zhan');
f.printName = function(){
console.log(this.name);
}
f.printName();//zhan 可以直接在这个对象中找到这个属性f.alertName();//alert弹出zhan 这时候在这个对象本身找不到这个属性，去Foo.prototype找,得到值/*******************************//*之前在牛可网碰到到一道面试题*/var A = {n:4399};var B = function(){
this.n = 9999;
}var C = function(){
var n = 8888;
}
B.prototype = A;
C.prototype = A;var b = new B();var c = new C();
A.n++;
console.log(b.n);//9999console.log(c.n);//4400//先从他的实例中找，找不到去它的构造函数的prototype中找this
For the above test code, it always points to the object itself, so executing f.alertName
can pop up zhan
The properties of the loop itself
Still for the above test code, if you loop, you can find the name attribute, alertName attribute, and printName attribute. But in general, we only want to get the attributes defined by the object itself, such as ：name attribute and printName attribute
var itemfor(item in f){ if(f.hasOwnProperty(item)){
console.log(item); // 高级浏览器已经在forin中屏蔽了来自原型的属性
//但在这里建议大家还是加上这个判断，保证程序的健壮性（程序对于规范要求以外的输入情况的处理能力）
}
}Related recommendations:
Instance analysis js prototype and call()
JS prototype Four steps of inheritance
7 recommended articles about js prototype chain
The above is the detailed content of Detailed explanation of JS prototype. For more information, please follow other related articles on the PHP Chinese website!
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
Detailed explanation of obtaining administrator rights in Win11
Mar 08, 2024 pm 03:06 PM
Windows operating system is one of the most popular operating systems in the world, and its new version Win11 has attracted much attention. In the Win11 system, obtaining administrator rights is an important operation. Administrator rights allow users to perform more operations and settings on the system. This article will introduce in detail how to obtain administrator permissions in Win11 system and how to effectively manage permissions. In the Win11 system, administrator rights are divided into two types: local administrator and domain administrator. A local administrator has full administrative rights to the local computer
Detailed explanation of division operation in Oracle SQL
Mar 10, 2024 am 09:51 AM
Detailed explanation of division operation in OracleSQL In OracleSQL, division operation is a common and important mathematical operation, used to calculate the result of dividing two numbers. Division is often used in database queries, so understanding the division operation and its usage in OracleSQL is one of the essential skills for database developers. This article will discuss the relevant knowledge of division operations in OracleSQL in detail and provide specific code examples for readers' reference. 1. Division operation in OracleSQL
Detailed explanation of the linux system call system() function
Feb 22, 2024 pm 08:21 PM
Detailed explanation of Linux system call system() function System call is a very important part of the Linux operating system. It provides a way to interact with the system kernel. Among them, the system() function is one of the commonly used system call functions. This article will introduce the use of the system() function in detail and provide corresponding code examples. Basic Concepts of System Calls System calls are a way for user programs to interact with the operating system kernel. User programs request the operating system by calling system call functions
Detailed explanation of the role and usage of PHP modulo operator
Mar 19, 2024 pm 04:33 PM
The modulo operator (%) in PHP is used to obtain the remainder of the division of two numbers. In this article, we will discuss the role and usage of the modulo operator in detail, and provide specific code examples to help readers better understand. 1. The role of the modulo operator In mathematics, when we divide an integer by another integer, we get a quotient and a remainder. For example, when we divide 10 by 3, the quotient is 3 and the remainder is 1. The modulo operator is used to obtain this remainder. 2. Usage of the modulo operator In PHP, use the % symbol to represent the modulus
Simple JavaScript Tutorial: How to Get HTTP Status Code
Jan 05, 2024 pm 06:08 PM
JavaScript tutorial: How to get HTTP status code, specific code examples are required. Preface: In web development, data interaction with the server is often involved. When communicating with the server, we often need to obtain the returned HTTP status code to determine whether the operation is successful, and perform corresponding processing based on different status codes. This article will teach you how to use JavaScript to obtain HTTP status codes and provide some practical code examples. Using XMLHttpRequest
Detailed explanation of Linux curl command
Feb 21, 2024 pm 10:33 PM
Detailed explanation of Linux's curl command Summary: curl is a powerful command line tool used for data communication with the server. This article will introduce the basic usage of the curl command and provide actual code examples to help readers better understand and apply the command. 1. What is curl? curl is a command line tool used to send and receive various network requests. It supports multiple protocols, such as HTTP, FTP, TELNET, etc., and provides rich functions, such as file upload, file download, data transmission, proxy
Learn more about Promise.resolve()
Feb 18, 2024 pm 07:13 PM
Detailed explanation of Promise.resolve() requires specific code examples. Promise is a mechanism in JavaScript for handling asynchronous operations. In actual development, it is often necessary to handle some asynchronous tasks that need to be executed in sequence, and the Promise.resolve() method is used to return a Promise object that has been fulfilled. Promise.resolve() is a static method of the Promise class, which accepts a
Detailed explanation of numpy version query method
Jan 19, 2024 am 08:20 AM
Numpy is a Python scientific computing library that provides a wealth of array operation functions and tools. When upgrading the Numpy version, you need to query the current version to ensure compatibility. This article will introduce the method of Numpy version query in detail and provide specific code examples. Method 1: Use Python code to query the Numpy version. You can easily query the Numpy version using Python code. The following is the implementation method and sample code: importnumpyasnpprint(np
