Protecting Your Self-Written JavaScript Code from Unauthorized Use

To prevent others from directly "stealing" or unauthorized use of your JavaScript code, which is inherently executed on the client-side and can be viewed and modified by users, you can employ several strategies. Here is a translation of the previous answer into English:

1. Code Obfuscation:
   Use tools like JShaman or JS-Obfuscator to obfuscate your JavaScript code, making it difficult to read and understand. This won't deter a determined attacker, but it can deter most casual users.

2. Code Splitting and Modularization:
   Split your code into multiple modules and utilize modern front-end frameworks (such as React, Vue, Angular) and bundlers (like Webpack, Rollup) for packaging. This way, even if someone views the source code, they'll find it challenging to trace and understand the relationships between various parts.

3. Copyright Notice and Licensing:
   Include a copyright notice and licensing information at the top of your code, specifying the type of license you're using (e.g., MIT, Apache, etc.). This won't prevent code theft, but it provides legal protection and clarifies how you want your code to be used.

4. Access Control and Authentication:
   If your code relies on backend APIs or services, ensure these APIs or services are protected with appropriate access control and authentication. This way, even if someone gets your frontend code, they can't interact with the backend without proper credentials.

5. Encrypt Sensitive Data:
   Do not hardcode any sensitive data (such as API keys, passwords) in your frontend code. Instead, use secure backend mechanisms (such as HTTPS and OAuth) to transmit and validate such data.

6. Use CDN and Version Control:
   Serve your JavaScript code through a CDN (Content Delivery Network) and utilize version control to manage different versions. This makes it easier to track and manage the distribution and usage of your code.

7. Monitoring and Alerts:
   Use web analytics tools and logging to monitor the usage of your code. Set up alerts to notify you of abnormal behavior, such as excessive requests from unknown sources or unusual API call patterns.

8. Limit Functionality:
   If possible, restrict certain critical functionalities to only authenticated and authorized users. This can be achieved through backend validation, user session management, or frontend token systems.

9. Legal Measures:
   If you believe your code is being used or distributed illegally, you can consider taking legal action to protect your rights. This includes suing infringers, seeking compensation, or obtaining injunctions.

Please note that no method can completely prevent unauthorized use of your code. The strategies mentioned above are only meant to mitigate such risks. Always consider security and privacy best practices when writing and distributing your code.