Code examples of using JavaScript in HTML-JS Tutorial-php.cn

Home

Web Front-end

JS Tutorial

Code examples of using JavaScript in HTML

巴扎黑

Aug 11, 2017 pm 03:44 PM

htmljavascriptjs

This article mainly introduces the use of JavaScript example code in HTML. Friends who need it can refer to the

##<script> tag<strong></script>

In HTML5, script mainly has the following attributes: async, defer, charset, src, type,

async (optional):

Keywords: asynchronous script, external file, immediate download;

When the tag contains this attribute, the script (external file) will be downloaded immediately. It is only valid for external script files. The page can be downloaded at the same time. For other operations, parsing and execution will stop after the download is completed, and parsing will continue after execution, but the execution order cannot be guaranteed.

<script src="js/index2.js" async="async"></script>

#defer (optional):

Keywords: delay script, external file, delay Loading;

When the tag contains this attribute, the script can wait until the page is completely parsed or displayed before execution. It is only valid for external files. If there are two scripts with defer at the same time, due to delay , the former will be limited to the execution of the latter.

<script src="js/index1.js" defer="defer"></script>

charset (optional):

Keywords: character set

Most browsers have ignored its value, so few people use it.

src (optional):

Keywords: external reference

Represents the address of the external file that needs to be referenced.

type (optional):

Keywords: MIME (scripting language content type)

To ensure maximum Compatible with limited browsers, the type attribute value is mainly text/javascript. If this attribute is not written, its default value is still text/javascript.

Note: When referencing external files, do not add other JS code to the tag. When parsing, the browser will only download the external script file referenced by src, and the code embedded in the table will be ignored. .

## <script>Location of tags<span style="color: #ff0000"><strong> Usually, we place tags with external files (including CSS files , JavaScript files) are placed in the same location, usually inside the <head> tag. </script>

But once multiple JavaScript external files are encountered during the parsing process, the page cannot be fully displayed until all external files are loaded, so usually we will put it in the

tag at the bottom, as shown below:

As mentioned above, there is a defer attribute in <script>, but since it is mentioned in HTML5, HTML5 will ignore it The defer attribute set by the embedded script is currently only supported by IE4~IE7. IE8 will fully follow the HTML5 standard from now on, so placing <script> at the bottom of the <body> tag is still the best choice. </script>

Advantages of referencing external files

The browser does not support scripts;

Browse The server supports scripts, but JavaScript is disabled;
If any of the above two conditions is met, the content within the

The page above gives the user a message, which will only be displayed when the browser does not support or disables JavaScript, otherwise the user will never see it and will not Will affect the display of other elements on the page.

The above is the detailed content of Code examples of using JavaScript in HTML. For more information, please follow other related articles on the PHP Chinese website!

Statement

The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

JavaScript Engines: Comparing ImplementationsApr 13, 2025 am 12:05 AM

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.

Beyond the Browser: JavaScript in the Real WorldApr 12, 2025 am 12:06 AM

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.

Building a Multi-Tenant SaaS Application with Next.js (Backend Integration)Apr 11, 2025 am 08:23 AM

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

How to Build a Multi-Tenant SaaS Application with Next.js (Frontend Integration)Apr 11, 2025 am 08:22 AM

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: Exploring the Versatility of a Web LanguageApr 11, 2025 am 12:01 AM

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.

The Evolution of JavaScript: Current Trends and Future ProspectsApr 10, 2025 am 09:33 AM

The latest trends in JavaScript include the rise of TypeScript, the popularity of modern frameworks and libraries, and the application of WebAssembly. Future prospects cover more powerful type systems, the development of server-side JavaScript, the expansion of artificial intelligence and machine learning, and the potential of IoT and edge computing.

Demystifying JavaScript: What It Does and Why It MattersApr 09, 2025 am 12:07 AM

JavaScript is the cornerstone of modern web development, and its main functions include event-driven programming, dynamic content generation and asynchronous programming. 1) Event-driven programming allows web pages to change dynamically according to user operations. 2) Dynamic content generation allows page content to be adjusted according to conditions. 3) Asynchronous programming ensures that the user interface is not blocked. JavaScript is widely used in web interaction, single-page application and server-side development, greatly improving the flexibility of user experience and cross-platform development.

Is Python or JavaScript better?Apr 06, 2025 am 12:14 AM

Python is more suitable for data science and machine learning, while JavaScript is more suitable for front-end and full-stack development. 1. Python is known for its concise syntax and rich library ecosystem, and is suitable for data analysis and web development. 2. JavaScript is the core of front-end development. Node.js supports server-side programming and is suitable for full-stack development.

See all articles

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

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)

3 weeks agoBy尊渡假赌尊渡假赌尊渡假赌

R.E.P.O. Best Graphic Settings

3 weeks agoBy尊渡假赌尊渡假赌尊渡假赌

Assassin's Creed Shadows: Seashell Riddle Solution

2 weeks agoByDDD

R.E.P.O. How to Fix Audio if You Can't Hear Anyone

3 weeks agoBy尊渡假赌尊渡假赌尊渡假赌

WWE 2K25: How To Unlock Everything In MyRise

4 weeks agoBy尊渡假赌尊渡假赌尊渡假赌

Hot Tools

mPDF

mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),