Is javascript safe?

javascript has security. JavaScript is a security language. It does not allow access to the local hard disk, cannot store data on the server, does not allow modification and deletion of network documents, and can only achieve information browsing or dynamic interaction through the browser; thus effectively to prevent data loss.

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

JavaScript ("JS" for short) is currently the most popular and widely used client-side scripting language. It is used to add some dynamic effects and interactive functions to web pages and plays a decisive role in the field of web development.

JavaScript is an event-driven scripting language that can respond to user input without using a web server. For example, when we visit a web page, we click or scroll through the web page with the mouse. When opening a window, JavaScript can respond directly to these events.

JavaScript does not depend on the operating system and can run in the browser. Therefore, after a JavaScript script is written, it can be run on any system, as long as the browser on the system supports JavaScript.

JavaScript is a security language. It does not allow access to the local hard disk, cannot store data on the server, does not allow modification and deletion of network documents, and can only browse information through a browser. Or dynamic interaction; thereby effectively preventing data loss.

5 Easy-to-implement JavaScript security best practices

1. Use JavaScript linter

The simplest and easiest way to avoid JavaScript security issues is to inspect your code. Linter is a static code analysis tool that checks your code for programming and style errors, code smells, and known security vulnerabilities.

The three most famous JavaScript linters are JSHint, JSLint and ESLint. Modern source code editors, such as Visual Studio Code and Atom, also come with pluggable JavaScript linting capabilities.

2. Avoid using inline JavaScript and establish a content security policy

Using inline script tags will make your website or application more vulnerable to cross-site scripting ( XSS) attacks. You can avoid this JavaScript security risk by adding all scripts, including inline event handlers (such as onclick), as external .js files.

For increased security, we also recommend that you establish a Content Security Policy (CSP). This is a security layer in the communication between client and server that allows you to add content security rules to HTTP response headers.

Setting up a more effective CSP is easier if you don’t have any inline scripts on your pages. You can use the script-src and default-src directives to block all inline scripts, so if any malicious inline script attempts to execute on your site, it will automatically fail.

3. Verify user input

Validating user input on both the client and server sides is crucial to avoid malicious code injection.

HTML5 forms come with built-in form validation attributes such as required, min, max, type, etc., allowing you to check user data and return error messages without using any JavaScript on the client side. You can also use the pattern HTML attribute to validate entered values ​​using regular expressions.

In addition to these HTML5 attributes, modern browsers also support the Constraint Validation API, which allows you to perform custom input validation using JavaScript.

This is a Web API that extends the JavaScript interfaces belonging to different HTML elements used in forms (such as HTMLInputElement, HTMLSelectElement and HTMLButtonElement) and provides useful properties and methods for different constraints Check input validity, report validity status, and perform other operations.

4. Escape or encode user input

To avoid XSS attacks, it is also important to escape or encode incoming or unsafe data. Escaping and encoding are two techniques for converting special characters that may pose a security risk into a safe form.

While encoding adds an extra character before a potentially dangerous character, such as the \ character before a quote in JavaScript, escaping converts the character into an equivalent but safe format, such as the > character to > String in HTML.

As a rule of thumb, you should always encode HTML entities (such as characters) when they come from an untrusted source. To escape URIs and JavaScript codes, you can use free escaping/encoding tools such as FreeFormatter's JavaScript String Escaper and URL Encoder/Decoder.

It's best to avoid using JavaScript properties and methods that return unescaped strings. For example, you can use the safe textContent property instead of innerHTML which parses to HTML (so the characters are not escaped).

5. Compress, bundle and obfuscate your JavaScript code

Finally, you can use tools like Webpack with more security features to minify and bundle your code, making it harder for hackers to understand the structure and logic of your scripts. For example, you could add a random number to every script it loads.

While minifying and bundling scripts are often considered JavaScript best practices, obfuscation is a controversial topic. This is because it takes longer for the browser to load the obfuscated script, which degrades performance and user experience, especially at higher obfuscation levels. However, if you still decide to obfuscate some or all of your scripts, you can use free tools like Obfuscator.io, which also has plugins for popular tools like Webpack, Grunt, Rollup, Netlify, and more.

Following these JavaScript security best practices can help you make your scripts more secure and prevent common attacks such as cross-site scripting, cross-site request forgery, third-party security vulnerabilities, and more.

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