


A brief discussion on JavaScript constructors and instantiated objects_Basic knowledge
Foreword--Let’s talk about it in front
I think there are many beginner friends who have rarely been exposed to backend programming languages before, just like me, they are confused about a series of "nouns" in JavaScript. It seems that I roughly know what it is about, but in fact I still don’t understand it clearly; I think that when learning any kind of knowledge, the first step should be to clarify the most basic terminology explanation (knowing what it is about will help us better understand it) (Understand it.) That is, knowing what it is and why it is, will be very helpful for future advanced learning. Below I will briefly talk about my own understanding of some seemingly unimportant but necessary knowledge points. (If there are any discrepancies, please correct me)
1. What is a constructor
Constructor is a special method. It is mainly used to initialize the object when creating the object, that is, to assign initial values to the object member variables. It is always used together with the new operator in the statement to create the object.
This is the explanation from Baidu Encyclopedia. The explanation is very bookish but the meaning is still very clear. Please see a small example below:
var request = new XMLHttpRequest();
This expression is often used when we create request objects when using AJAX technology. Then we can clearly see that "new XMLHttpRequest();" is a standard constructor! We declare a "request" object in "var" and use the constructor "new XMLHttpRequest();" to initialize the "request" object and assign it an initial value. So we can know: "The 'function' used with the 'new' operator to create and initialize the object is the constructor".
For example, our common way to declare an array is the standard constructor: var array = new Array();
2. What is an instantiated object
var request = new XMLHttpRequest();
In object-oriented programming, the process of creating objects using classes is usually called instantiation.
I highlighted the key points of the explanation in red and blue above. To put it bluntly, instantiating an object is the process of creating an object!
So what is "class"? According to the literal understanding, we can understand it as "type". For example, "cake" is a category of desserts, that is, a type; then cheesecake is a specific individual of the category of cake in desserts, that is, an object.
We know that in programming language, "class" is abstract. We have no way to operate it or use its methods and properties. Only by instantiating this class into an object can we call a series of it. methods and properties. In fact, this is also easy to understand. In life, we have no way to see or capture abstract things, so naturally we have no way to use some of its functions. We can only concrete the abstract things into each individual, individual or actual situation. Only when we have an object can we clearly understand or recognize it; the same is true for programming. Therefore, instantiating an object is a process from abstract to concrete, and this process is called instantiation.
The above is the entire content of this article, I hope you all like it.

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.

The main uses of JavaScript in web development include client interaction, form verification and asynchronous communication. 1) Dynamic content update and user interaction through DOM operations; 2) Client verification is carried out before the user submits data to improve the user experience; 3) Refreshless communication with the server is achieved through AJAX technology.


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