Detailed explanation of construction without new
This time I will bring you a detailed explanation of the new-free build. What are the precautions when using the new-free build? Here are actual cases, let’s take a look.
Preface
When we want tocreate an object, we may use the new method to construct an object, then It stands to reason that jquery is also an object and should be constructed using new jquery(). Why do we create jquery objects without using new jquery() but directly using something like $(ele)How to construct a jquery object? In fact, new is still used internally to build it, but jquery builds it for us internally. Please see the following code
function Jquery(selector, context) {
return new Jquery(selector, context);
}
Jquery.prototype = {
version:'1.01'
}Directly use new internally to build Jquery like this. Obviously there is a problem. In this case, it will form An infinite loop. In order to solve the problem of the infinite loop, please look at the following code:
function Jquery(selector, context) {
return Jquery.prototype.init(selector, context);
}
Jquery.prototype = {
version:'1.01',
init: function () {
this.name = "lin";
return this;
}
}
var a = Jquery();
var b = Jquery();
console.log(a.version); //1.01
console.log(a.name); //lin
a.name = "na";
console.log(b.name); //naThe problem of the infinite loop has indeed been solved, but new problems have been discovered. You can see that the attributes of the two objects a and b are common. I changed the a.name attribute to na, and the b.name attribute also changed to na. The reason is that this points to Jquery's
in order to solve this problem. , we can build a new object every time we call Jquery(). The improved code is as follows:
function Jquery(selector, context) {
return new Jquery.prototype.init(selector, context); //注意看，这里多了个new
}
Jquery.prototype = {
version:'1.01',
init: function () {
this.name = "lin";
console.log(this);
return this;
}
}
var a = Jquery();
var b = Jquery();
console.log(a.version); //undefined
console.log(a.name); //lin
a.name = "na";
console.log(b.name); //naAfter processing in this way, the problem of attribute sharing has been solved. Each object Each has its own attributes, which can be modified freely. Each object does not affect each other, but new problems have been discovered. You can see that when we print the a.version attribute on the console, we cannot read this attribute. The reason is that Jquery.prototype and Jquery.prototype.init.prototype are irrelevant at this time. What we create is the Jquery.prototype.init object. , so you can only read the properties on Jquery.prototype.init.prototype but cannot read the properties on Jquery.prototype (this example refers to the version property), solution The method is very simple, just assign Jquery.prototype to Jquery.prototype.init.prototype, which is equivalent to assigning all the properties on the Jquery prototype to Jquery.init On the prototype, please look at the following code:
function Jquery(selector, context) {
return new Jquery.prototype.init(selector, context);
}
Jquery.prototype = {
version:'1.01',
init: function () {
this.name = "lin";
return this;
}
}
Jquery.prototype.init.prototype = Jquery.prototype; //画龙点睛之笔
var a = Jquery();
var b = Jquery();
console.log(a.version); //1.01
console.log(a.name); //lin
a.name = "na";
console.log(b.name); //naAs you can see, our console prints the version attribute of the a object, which can be read and printed.
At this point, the new-free construction of Jquery has been completed.
ps: jQuery.fn is actually the prototype of jQuery. You can see this statement in the jquery source code: jQuery.fn = jQuery.prototype = { };
$() and jquery() are actually the same. You can see this statement in the jquery source code: window.jQuery = window.$ = jQuery;
Prototype prototype
Let’s understand what a prototype is?
In JavaScript, the prototype is also an object. The properties of the object can be realized through the prototype. Inheritance, JavaScript objects all contain a "[[ Prototype]]" internal property, this property corresponds to the prototype of the object.
The two attributes "prototype" and "proto" may sometimes be confused. "Person.prototype" and "Person.proto" are completely different.
Here is a brief introduction to "prototype" and "proto":
For all objects, there is a proto attribute, which corresponds to the prototype of the object.
For function objects, in addition to the proto attribute, there is also a prototype attribute. When a function is used as a constructor to create an instance, the prototype attribute value of the function will be used as the prototype. Assign values to all object instances (that is, set the proto attribute of the instance)
function Person(name, age){
this.name = name;
this.age = age;
}
Person.prototype.getInfo = function(){
console.log(this.name + " is " + this.age + " years old");
};
//调用
var will = new Person("Will", 28);
will.getInfo();//"Will is 28 years old"I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the PHP Chinese website!
Recommended reading:
How two zTree interact with each other
How to use webpack to write jquery environment configuration
How to automatically convert uppercase and lowercase letters when jackson parses a json string
Usage of jQuery EasyUI folding panel
The above is the detailed content of Detailed explanation of construction without new. 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
1655
14
1414
52
1307
25
1255
29
1228
24
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
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
Smooth build: How to correctly configure the Maven image address
Feb 20, 2024 pm 08:48 PM
Smooth build: How to correctly configure the Maven image address When using Maven to build a project, it is very important to configure the correct image address. Properly configuring the mirror address can speed up project construction and avoid problems such as network delays. This article will introduce how to correctly configure the Maven mirror address and give specific code examples. Why do you need to configure the Maven image address? Maven is a project management tool that can automatically build projects, manage dependencies, generate reports, etc. When building a project in Maven, usually
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
