


The execution process of javascript in the browser (picture and text)_javascript skills
1. The components of most browsers are as shown in the figure
(1) Network - used to complete network calls, such as http requests. It has a platform-independent interface and can work on different platforms
(2) UI backend - used to draw similar combination selections Basic components such as boxes and dialog boxes have a common interface that is not specific to a certain platform. The bottom layer uses the user interface of the operating system
(3) JS interpreter - used to interpret and execute JS code
ps: The above pictures and knowledge points are mainly from "HOW BROWSERS WORK: BEHIND THE SCENES OF MODERN WEB BROWSERS". Students who want to know more about it can focus on it.
2. Most browsers (such as Chrome) use a single thread to execute javascript and update the user interface. This thread, often called the "browser UI thread", can only perform one of these operations at a time, which means that the user interface cannot respond to input while the Javascript code is executing, and vice versa. This is done because the function of the javascript code is to operate the DOM and update the user interface. It can be more efficient to use the same thread to do these two things
3. The work of the browser UI thread is based on a simple queue system, and the tasks will be Save to queue until process is idle. Once free, the next task in the queue is re-extracted and run. These tasks either run JavaScript code or perform UI updates, including redrawing and reflowing.
4. It is important to emphasize that JavaScript runs in a single thread. Don’t be confused by functions such as setTimeout() and setInterVal() and mistakenly think that it is multi-threaded.
ok, the basic points have been explained, let us get to the point and explain the execution process of javascript in the browser.
1. Principle
Generally speaking, every time the <script> tag appears, it will overbearingly make the page wait for the parsing and execution of the script. Regardless of whether the current Javascript is embedded or contains an external link file, the page Both downloading and rendering must stop and wait for script execution to complete. This is necessary in the life cycle of the page, because the page content may be modified during script execution. A typical example is using document.write() in the page. <BR>When the javascript code is embedded in html, this is relatively easy to understand, but when the javascript is an external link file, it is a little bit more loaded, because there is a loading process, and the browser often loads the js file. Cache it. <BR>First, we use the following example to illustrate the caching problem<BR><div class="codetitle"><span><a style="CURSOR: pointer" data="13076" class="copybut" id="copybut13076" onclick="doCopy('code13076')"><U>Copy the code The code is as follows:<div class="codebody" id="code13076"> <BR><html> <BR><head> <BR><script type='text/javascript' src='js/f2.js'></script>
> ;

Python is more suitable for beginners, with a smooth learning curve and concise syntax; JavaScript is suitable for front-end development, with a steep learning curve and flexible syntax. 1. Python syntax is intuitive and suitable for data science and back-end development. 2. JavaScript is flexible and widely used in front-end and server-side programming.

Python and JavaScript have their own advantages and disadvantages in terms of community, libraries and resources. 1) The Python community is friendly and suitable for beginners, but the front-end development resources are not as rich as JavaScript. 2) Python is powerful in data science and machine learning libraries, while JavaScript is better in front-end development libraries and frameworks. 3) Both have rich learning resources, but Python is suitable for starting with official documents, while JavaScript is better with MDNWebDocs. The choice should be based on project needs and personal interests.

The shift from C/C to JavaScript requires adapting to dynamic typing, garbage collection and asynchronous programming. 1) C/C is a statically typed language that requires manual memory management, while JavaScript is dynamically typed and garbage collection is automatically processed. 2) C/C needs to be compiled into machine code, while JavaScript is an interpreted language. 3) JavaScript introduces concepts such as closures, prototype chains and Promise, which enhances flexibility and asynchronous programming capabilities.

Different JavaScript engines have different effects when parsing and executing JavaScript code, because the implementation principles and optimization strategies of each engine differ. 1. Lexical analysis: convert source code into lexical unit. 2. Grammar analysis: Generate an abstract syntax tree. 3. Optimization and compilation: Generate machine code through the JIT compiler. 4. Execute: Run the machine code. V8 engine optimizes through instant compilation and hidden class, SpiderMonkey uses a type inference system, resulting in different performance performance on the same code.

JavaScript's applications in the real world include server-side programming, mobile application development and Internet of Things control: 1. Server-side programming is realized through Node.js, suitable for high concurrent request processing. 2. Mobile application development is carried out through ReactNative and supports cross-platform deployment. 3. Used for IoT device control through Johnny-Five library, suitable for hardware interaction.

I built a functional multi-tenant SaaS application (an EdTech app) with your everyday tech tool and you can do the same. First, what’s a multi-tenant SaaS application? Multi-tenant SaaS applications let you serve multiple customers from a sing

This article demonstrates frontend integration with a backend secured by Permit, building a functional EdTech SaaS application using Next.js. The frontend fetches user permissions to control UI visibility and ensures API requests adhere to role-base

JavaScript is the core language of modern web development and is widely used for its diversity and flexibility. 1) Front-end development: build dynamic web pages and single-page applications through DOM operations and modern frameworks (such as React, Vue.js, Angular). 2) Server-side development: Node.js uses a non-blocking I/O model to handle high concurrency and real-time applications. 3) Mobile and desktop application development: cross-platform development is realized through ReactNative and Electron to improve development efficiency.


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

SublimeText3 Chinese version
Chinese version, very easy to use

ZendStudio 13.5.1 Mac
Powerful PHP integrated development environment

Zend Studio 13.0.1
Powerful PHP integrated development environment

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.

Atom editor mac version download
The most popular open source editor