JavaScript is a flexible programming language that is widely used in web development, mobile applications, and server-side programming. It can enhance the interactivity and dynamics of web pages, making users more comfortable, rich and faster when browsing web pages. However, for JavaScript to be executed correctly by the browser, it must be placed in the correct location.
JavaScript setting location
There are three main JavaScript setting locations:
1. Inline setting
Inline setting is to embed JavaScript code directly Into the tags in the HTML document, the method is relatively simple, but it is not recommended because it will seriously affect the readability and maintainability of the HTML document.
For example:
<button onclick="alert('Hello, World!')">Click?me!</button>
When this button is clicked, a warning box will pop up.
2. Internal settings
This setting method is to write JavaScript code in the <head>
or <body>
of the HTML document Within the <script>
tag in the tag. This setting can be placed either in the header or in the body part. The advantage of internal settings is that it can improve the readability and maintainability of HTML documents. In some cases, it can improve the access speed of the website because the js code will be cached, thereby reducing the pressure on the server.
For example:
<html> ??<head> ????<script type="text/javascript"> ??????function?greeting()?{ ????????alert('Hello,?World!'); ??????} ????</script> ??</head> ??<body> ????<button onclick="greeting()">Say?hello</button> ??</body> </html>
This script is defined at the head of the document, but used in the body of the document.
3. External settings
This setting method is to write the JavaScript code in a separate <.js>
file, and use <script> ;
tags are introduced into HTML documents. This setting method can achieve code reuse and overall optimization, and is more suitable for large websites and websites that require frequent updates.
For example: The HTML document structure is as follows
<!DOCTYPE html> <html> ??<head> ????<script src="script.js"></script> ??</head> ??<body> ????<button onclick="greeting()">Say?hello</button> ??</body> </html><p> Among them, the src attribute of the <code><script></code> tag specifies the introduction of a JavaScript file. The content of the file is as follows </p> <pre class="brush:php;toolbar:false">function?greeting()?{ ??alert('Hello,?World!'); }
This script exists alone in the external script.js
file.
Summary
No matter which method is used, it should be placed in <body>
or <head>
(preferably in <body>
) so that the browser can correctly parse and execute JavaScript code. When there is a lot of JavaScript code, it is recommended to use external settings to improve the maintainability and overall performance of the code. At the same time, we also need to pay attention to compatibility issues. Different browsers may parse and execute the same piece of JavaScript code differently.
The above is the detailed content of Where are the JavaScript settings. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undress AI Tool
Undress images for free

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

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

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

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

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

Hot Topics

React itself does not directly manage focus or accessibility, but provides tools to effectively deal with these issues. 1. Use Refs to programmatically manage focus, such as setting element focus through useRef; 2. Use ARIA attributes to improve accessibility, such as defining the structure and state of tab components; 3. Pay attention to keyboard navigation to ensure that the focus logic in components such as modal boxes is clear; 4. Try to use native HTML elements to reduce the workload and error risk of custom implementation; 5. React assists accessibility by controlling the DOM and adding ARIA attributes, but the correct use still depends on developers.

Shallowrenderingtestsacomponentinisolation,withoutchildren,whilefullrenderingincludesallchildcomponents.Shallowrenderingisgoodfortestingacomponent’sownlogicandmarkup,offeringfasterexecutionandisolationfromchildbehavior,butlacksfulllifecycleandDOMinte

StrictMode does not render any visual content in React, but it is very useful during development. Its main function is to help developers identify potential problems, especially those that may cause bugs or unexpected behavior in complex applications. Specifically, it flags unsafe lifecycle methods, recognizes side effects in render functions, and warns about the use of old string refAPI. In addition, it can expose these side effects by intentionally repeating calls to certain functions, thereby prompting developers to move related operations to appropriate locations, such as the useEffect hook. At the same time, it encourages the use of newer ref methods such as useRef or callback ref instead of string ref. To use Stri effectively

Create TypeScript-enabled projects using VueCLI or Vite, which can be quickly initialized through interactive selection features or using templates. Use tags in components to implement type inference with defineComponent, and it is recommended to explicitly declare props and emits types, and use interface or type to define complex structures. It is recommended to explicitly label types when using ref and reactive in setup functions to improve code maintainability and collaboration efficiency.

There are three key points to be mastered when processing Vue forms: 1. Use v-model to achieve two-way binding and synchronize form data; 2. Implement verification logic to ensure input compliance; 3. Control the submission behavior and process requests and status feedback. In Vue, form elements such as input boxes, check boxes, etc. can be bound to data attributes through v-model, such as automatically synchronizing user input; for multiple selection scenarios of check boxes, the binding field should be initialized into an array to correctly store multiple selected values. Form verification can be implemented through custom functions or third-party libraries. Common practices include checking whether the field is empty, using a regular verification format, and displaying prompt information when errors are wrong; for example, writing a validateForm method to return the error message object of each field. You should use it when submitting

Server-siderendering(SSR)inNext.jsgeneratesHTMLontheserverforeachrequest,improvingperformanceandSEO.1.SSRisidealfordynamiccontentthatchangesfrequently,suchasuserdashboards.2.ItusesgetServerSidePropstofetchdataperrequestandpassittothecomponent.3.UseSS

Vite or VueCLI depends on project requirements and development priorities. 1. Startup speed: Vite uses the browser's native ES module loading mechanism, which is extremely fast and cold-start, usually completed within 300ms, while VueCLI uses Webpack to rely on packaging and is slow to start; 2. Configuration complexity: Vite starts with zero configuration, has a rich plug-in ecosystem, which is suitable for modern front-end technology stacks, VueCLI provides comprehensive configuration options, suitable for enterprise-level customization but has high learning costs; 3. Applicable project types: Vite is suitable for small projects, rapid prototype development and projects using Vue3, VueCLI is more suitable for medium and large enterprise projects or projects that need to be compatible with Vue2; 4. Plug-in ecosystem: VueCLI is perfect but has slow updates,

Content Security Policy (CSP) prevents attacks such as XSS by limiting the loading source of web page resources. Its core mechanism is to set a whitelist to prevent unauthorized scripts from being executed. The steps to enable include: 1. Define the policy and clarify the allowed resource sources; 2. Add Content-Security-PolicyHTTP header to the server; 3. Use Report-Only mode to test and debug in the initial stage; 4. Continuous monitoring and optimization strategies to ensure that they do not affect normal functions. Notes include handling inline scripts, careful use of third-party resources, compatibility support, and other irreplaceable security measures.
