Security is a broad aspect and should be considered on more levels than just the language you are using. However, since JavaScript is most often used for web-based applications, it requires some special attention.

Here are some aspects that will help you increase the security of your JavaScript applications:

• Ensure that input from the application’s users is always validated and sanitised.
• Implement strong authentication and authorisation mechanisms and rely on common practices such as OAuth2.
• For network communication, HTTPS is recommended. Some JavaScript APIs won’t even work if the website isn’t loaded over HTTPS!
• Regularly update your dependencies. Tools like npm audit can help you detect outdated dependencies and possible vulnerabilities.