What practices should I follow to secure sensitive data, such as API keys and database credentials, when building a JavaScript-based single-page application (SPA)?

When building a JavaScript SPA, it's crucial to never expose sensitive data like API keys or database credentials on the client side. So, make sure to store such information on the server and access it via secure and authenticated APIs. You can use environment variables to manage sensitive data on the server side. Moreover, make sure to implement robust authentication and authorization mechanisms to restrict access to these APIs. Additionally, ensure all data transmission is encrypted using HTTPS to prevent data interception. Last but not least, remember to regularly review and update your security practices to protect against emerging threats.