How can you prevent XSS attacks in a JavaScript application?

At the core of preventing XSS attacks is the principle of treating all user input as untrusted. This means that any data received from users should be sanitized and escaped before being rendered in the browser. Sanitization involves stripping out potentially malicious code from user inputs, whereas escaping transforms input into a secure format that ensures that any potentially executable code is not run by the browser. For instance, converting special characters like < into their HTML entity equivalents like &lt; effectively prevents script injection.

Another strategy I've implemented successfully in my projects is the use of Content Security Policy (CSP). CSP is a powerful tool that helps to detect and mitigate certain types of attacks, including XSS and data...