Regarding the JS scope issue, it is an interview question that interviewers never tire of asking during interviews. Sometimes it is really frustrating. The following article mainly shares with you javascriptSome common interview questions about scope, friends in need can refer to them. Let’s take a look below.
Recommended related articles:The most complete collection of js interview questions in 2020 (latest)
This article mainly shares with you the relevant content about the JavaScript scope interview questions, and shares it for your reference and study. Let’s take a look together.
1. Scope:
Before understanding scope, you first need to understand some basic concepts:
Every variable, function has its scope, and it cannot be used beyond the scope. This is called scope.
2. Global variables, local variables:
1. Global variables:
(1) Variables declared in the global scope, such as var a=1;
(2) Only assigned values without declaration, such as a= 2;
(Note: If a=2 is in the function environment, it is also a global variable)
2. Local variables:
Variables written into functions are called local variables.
3. Function:
(1) Program safety.
(2) Release of memory.
3. Scope chain:
The process of finding the quantity. First, check whether there is a declaration or function in your local environment. If there is, check whether the declaration has an assignment or the content of the function. If not, search up one level.
4. Pre-parsing sequence:
Every program has to do the work. The program starts by pre-parsing the grammar and whether there are punctuation marks. If there is an error, analyze whether the memory can be accommodated, analyze the variables... until the analysis is correct, start to follow the normal process sequence. Just imagine, if there is no pre-parsing sequence and the process sequence is followed directly, the program may execute until the last function, find syntax error, and then start to report errors. How bad will the performance be!
Sequential content:
The above is the detailed content of Common interview questions about JavaScript. For more information, please follow other related articles on the PHP Chinese website!

JavaScript runs in browsers and Node.js environments and relies on the JavaScript engine to parse and execute code. 1) Generate abstract syntax tree (AST) in the parsing stage; 2) convert AST into bytecode or machine code in the compilation stage; 3) execute the compiled code in the execution stage.

The future trends of Python and JavaScript include: 1. Python will consolidate its position in the fields of scientific computing and AI, 2. JavaScript will promote the development of web technology, 3. Cross-platform development will become a hot topic, and 4. Performance optimization will be the focus. Both will continue to expand application scenarios in their respective fields and make more breakthroughs in performance.

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.


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

Dreamweaver CS6
Visual web development tools

SublimeText3 Linux new version
SublimeText3 Linux latest version

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

MantisBT
Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.

Atom editor mac version download
The most popular open source editor
