js中继承可以分为两种:对象冒充和原型链方式
一、对象冒充包括三种:临时属性方式、call()及apply()方式
1.临时属性方式
function Person(name){
this.name = name;
this.say = function(){
alert('My name is '+this.name);
}
}
function F2E(name,id){
this.temp = Person;
this.temp(name);
delete this.temp;
this.id = id;
this.showId = function(){
alert('Good morning,Sir,My work number is '+this.id);
}
}
var simon = new F2E('Simon',9527);
simon.say();
simon.showId();
2.call()/apply()方式
实质上是改变了this指针的指向
function Person(name){
this.name = name;
this.say = function(){
alert('My name is '+this.name);
}
}
function F2E(name,id){
Person.call(this,name); //apply()方式改成Person.apply(this,new Array(name));
this.id = id;
this.showId = function(){
alert('Good morning,Sir,My work number is '+this.id);
}
}
var simon = new F2E('Simon',9527);
simon.say();
simon.showId();
缺点:先来看这么一张内存分配图:
![]() |
在OO概念中,new实例化后,对象就在堆内存中形成了自己的空间,值得注意的是,这个代码段。而成员方法就是存在这个代码段的,并且方法是共用的。问题就在这里,通过对象冒充方式继承时,所有的成员方法都是指向this的,也就是说new之后,每个实例将都会拥有这个成员方法,并不是共用的,这就造成了大量的内存浪费。并且通过对象冒充的方式,无法继承通过prototype方式定义的变量和方法,如以下代码将会出错:
function Person(name){
this.name = name;
this.say = function(){
alert('My name is '+this.name);
}
}
Person.prototype.age = 20;
Person.prototype.sayAge = function(){alert('My age is '+this.age)};
function F2E(name,id){
Person.apply(this,new Array(name));
this.id = id;
this.showId = function(){
alert('Good morning,Sir,My work number is '+this.id);
}
}
var simon = new F2E('Simon',9527);
simon.sayAge(); //提示TypeError: simon.sayAge is not a function
二、原型链方式
function Person(){
this.name = 'Simon';
}
Person.prototype.say = function(){
alert('My name is '+this.name);
}
function F2E(id){
this.id = id;
this.showId = function(){
alert('Good morning,Sir,My work number is '+this.id);
}
}
F2E.prototype = new Person();
var simon = new F2E(9527);
simon.say();
simon.showId();
alert(simon.hasOwnProperty('id')); //检查是否为自身属性
接下来按照上面的例子来理解以下js原型链概念:
![]() |
The prototype chain can be understood as: each object in js has a hidden __proto__ attribute. The __proto__ attribute of an instantiated object points to the prototype method of its class, and this prototype method can be assigned to another An instantiated object, the __proto__ of this object needs to point to its class, thus forming a chain, that is,
Let’s talk about the disadvantages:
The disadvantage is obvious. The prototype chain inheritance means that parameters cannot be passed to the parent class when instantiating the subclass, which is why there is no function Person() in this example. Parameters, but directly written as this.name="Simon". The following code will not achieve the expected results:
this.name = name;
}
Person.prototype.say = function(){
alert('My name is ' this.name);
}
function F2E(name,id){
this.id = id;
this.showId = function(){
alert('Good morning,Sir,My work number is ' this .id);
}
}
F2E.prototype = new Person();
var simon = new F2E("Simon",9527);
simon.say( );
simon.showId();
function Person(name){
this.name = name;
}
Person.prototype.say = function(){
alert('My name is ' this.name);
}
function F2E(name,id){
this.id = id;
this.showId = function(){
alert('Good morning,Sir,My work number is ' this.id);
}
}
F2E.prototype = new Person( ); //Value cannot be passed here, neither this.name nor name will work. It is possible to directly write F2E.prototype = new Person('wood'), but in this case simon.say() will become My name is wood
var simon = new F2E("Simon",9527);
simon.say(); //Pop up My name is undefined
simon.showId();
Finally, let’s summarize what we think is a better way to implement inheritance. Member variables use object impersonation, and member methods use prototype chaining. The code is as follows:
this.name = name;
}
Person .prototype.say = function(){
alert('My name is ' this.name);
}
function F2E(name,id){
Person.call(this ,name);
this.id = id;
}
F2E.prototype = new Person();
//Note one detail here, showId cannot be written in F2E.prototype = new Person(); front
F2E.prototype.showId = function(){
alert('Good morning,Sir,My work number is ' this.id);
}
var simon = new F2E("Simon",9527);
simon.say();
simon.showId();

Detailed explanation of JavaScript string replacement method and FAQ This article will explore two ways to replace string characters in JavaScript: internal JavaScript code and internal HTML for web pages. Replace string inside JavaScript code The most direct way is to use the replace() method: str = str.replace("find","replace"); This method replaces only the first match. To replace all matches, use a regular expression and add the global flag g: str = str.replace(/fi

Leverage jQuery for Effortless Web Page Layouts: 8 Essential Plugins jQuery simplifies web page layout significantly. This article highlights eight powerful jQuery plugins that streamline the process, particularly useful for manual website creation

So here you are, ready to learn all about this thing called AJAX. But, what exactly is it? The term AJAX refers to a loose grouping of technologies that are used to create dynamic, interactive web content. The term AJAX, originally coined by Jesse J

This post compiles helpful cheat sheets, reference guides, quick recipes, and code snippets for Android, Blackberry, and iPhone app development. No developer should be without them! Touch Gesture Reference Guide (PDF) A valuable resource for desig

jQuery is a great JavaScript framework. However, as with any library, sometimes it’s necessary to get under the hood to discover what’s going on. Perhaps it’s because you’re tracing a bug or are just curious about how jQuery achieves a particular UI

10 fun jQuery game plugins to make your website more attractive and enhance user stickiness! While Flash is still the best software for developing casual web games, jQuery can also create surprising effects, and while not comparable to pure action Flash games, in some cases you can also have unexpected fun in your browser. jQuery tic toe game The "Hello world" of game programming now has a jQuery version. Source code jQuery Crazy Word Composition Game This is a fill-in-the-blank game, and it can produce some weird results due to not knowing the context of the word. Source code jQuery mine sweeping game

Article discusses creating, publishing, and maintaining JavaScript libraries, focusing on planning, development, testing, documentation, and promotion strategies.

This tutorial demonstrates how to create a captivating parallax background effect using jQuery. We'll build a header banner with layered images that create a stunning visual depth. The updated plugin works with jQuery 1.6.4 and later. Download the


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

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

EditPlus Chinese cracked version
Small size, syntax highlighting, does not support code prompt function

SublimeText3 Chinese version
Chinese version, very easy to use

DVWA
Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool

Dreamweaver CS6
Visual web development tools
