


Detailed explanation of examples of Class objects for getting started with ECMAScript6
This article mainly introduces the detailed introduction to ECMAScript6 introduction-Class object. The editor thinks it is quite good. Now I will share it with you and give you a reference. Let’s follow the editor and take a look.
Object-oriented languages have a sign, that is, they all have the concept of classes, through which any number of objects with the same properties and methods can be created.
There is no concept of class in ECMAScript5, so its objects are different from those in class-based languages.
The traditional way of generating objects in Javascript is through constructors
function Person(name, age){ this.name = name; this.age = age; this.sayHello = function(){ return "Hello "+ this.name; } } var person = new Person("dahan",18); person.sayHello(); //Hello dahan
The above method is the same as the form of declaring methods in Javascript, so the distinction between objects and methods is not obvious. It's easy to get confused.
ES6 introduces the concept of Class
(class). When we create objects through ES6 syntax, we can use the keyword class
like Java syntax. Used to define classes. Of course, the functions of this syntax can also be realized through ES5. It just makes the definition of classes clearer and easier to understand.
//类的定义 class Person { //ES6中新型构造器 constructor(name) { this.name = name; } //实例方法 sayName() { console.log("我的名字叫"+ this.name); } } //类的继承 class Programmer extends Person { constructor(name) { //直接调用父类构造器进行初始化 super(name); } program() { cosnole.log("这是我的地盘"); } } //运行测试 var person = new Person('lingxiao'); var coder = new Programmer('coder'); person.sayName(); //我的名字叫lingxiao coder.sayName(); //我的名字叫coder coder.program(); //这是我的地盘
Let’s pay attention to the syntax that appears in the above code.
constructor
constructor
is the default method of the class, just like the main method in Java, every class must have constructor
method.
When instantiating an object through new
, the constructor
method will be automatically called, and the value returned is the value returned by constructor
. constructor
By default, the instance object of the current class is returned (this)
, but we can also specify another object. Of course, this will result in the instantiated object not being of the current class. Example.
class Person { constructor(){ var ob = new Object(); return Ob; } sayHello(){ return "Hello World" } } var person = new Person(); person.sayHello(); //Uncaught TypeError: person.sayHello is not a function
When we instantiate an object, ES6 stipulates that I use the new keyword. If it is called directly, it will be called as a function.
class Person { constructor(name){ this.name = name; } }; var person = Person("dahan"); //Uncaught TypeError: Class constructor Person4 cannot be invoked without 'new'
this
In the first code, we saw this. This points to the instance itself in the class, but if we are in the method of the class If this is used, an error will occur when this method is called alone.
class Person{ constructor(name){ this.name = name; } sayHello() { return "Hello "+this.name } } var person = new Person("dahan"); var sayHello = person.sayHello; sayHello(); //Uncaught TypeError: Cannot read property 'name' of undefined
For this we can simply bind it in the constructor this
class Person{ constructor(name){ this.name = name; this.sayHello = this.sayHello.call(this); } sayHello() { return "Hello "+this.name } }
Inherit extend
We want If you want to extend some attributes on a class without modifying the original class, you use inheritance.
//类的继承 class Programmer extends Person { constructor(name,age) { this.age = age;//报错 //直接调用父类构造器进行初始化 super(name); } program() { cosnole.log("这是我的地盘"); } }
When using inheritance, you need to use the super
keyword to call the parent class, super(name)
just call the parent class’s constructor
method.
In addition, when we use inheritance, the super
keyword also helps us change the direction of this
, so we must first call super
method before using this
. ES6 requires that the constructor of a subclass must execute the super
function once, otherwise an error will be reported.
Finally
class
The appearance of the keyword also makes Javascript look more like an object-oriented language. I hope Javascript will get better and better. Easy to use.
The above is the detailed content of Detailed explanation of examples of Class objects for getting started with ECMAScript6. For more information, please follow other related articles on the PHP Chinese website!

Both Python and JavaScript's choices in development environments are important. 1) Python's development environment includes PyCharm, JupyterNotebook and Anaconda, which are suitable for data science and rapid prototyping. 2) The development environment of JavaScript includes Node.js, VSCode and Webpack, which are suitable for front-end and back-end development. Choosing the right tools according to project needs can improve development efficiency and project success rate.

Yes, the engine core of JavaScript is written in C. 1) The C language provides efficient performance and underlying control, which is suitable for the development of JavaScript engine. 2) Taking the V8 engine as an example, its core is written in C, combining the efficiency and object-oriented characteristics of C. 3) The working principle of the JavaScript engine includes parsing, compiling and execution, and the C language plays a key role in these processes.

JavaScript is at the heart of modern websites because it enhances the interactivity and dynamicity of web pages. 1) It allows to change content without refreshing the page, 2) manipulate web pages through DOMAPI, 3) support complex interactive effects such as animation and drag-and-drop, 4) optimize performance and best practices to improve user experience.

C and JavaScript achieve interoperability through WebAssembly. 1) C code is compiled into WebAssembly module and introduced into JavaScript environment to enhance computing power. 2) In game development, C handles physics engines and graphics rendering, and JavaScript is responsible for game logic and user interface.

JavaScript is widely used in websites, mobile applications, desktop applications and server-side programming. 1) In website development, JavaScript operates DOM together with HTML and CSS to achieve dynamic effects and supports frameworks such as jQuery and React. 2) Through ReactNative and Ionic, JavaScript is used to develop cross-platform mobile applications. 3) The Electron framework enables JavaScript to build desktop applications. 4) Node.js allows JavaScript to run on the server side and supports high concurrent requests.

Python is more suitable for data science and automation, while JavaScript is more suitable for front-end and full-stack development. 1. Python performs well in data science and machine learning, using libraries such as NumPy and Pandas for data processing and modeling. 2. Python is concise and efficient in automation and scripting. 3. JavaScript is indispensable in front-end development and is used to build dynamic web pages and single-page applications. 4. JavaScript plays a role in back-end development through Node.js and supports full-stack development.

C and C play a vital role in the JavaScript engine, mainly used to implement interpreters and JIT compilers. 1) C is used to parse JavaScript source code and generate an abstract syntax tree. 2) C is responsible for generating and executing bytecode. 3) C implements the JIT compiler, optimizes and compiles hot-spot code at runtime, and significantly improves the execution efficiency of JavaScript.

JavaScript's application in the real world includes front-end and back-end development. 1) Display front-end applications by building a TODO list application, involving DOM operations and event processing. 2) Build RESTfulAPI through Node.js and Express to demonstrate back-end applications.


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

SublimeText3 Mac version
God-level code editing software (SublimeText3)

MinGW - Minimalist GNU for Windows
This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

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

SublimeText3 Chinese version
Chinese version, very easy to use

Notepad++7.3.1
Easy-to-use and free code editor
