Can you explain what is meant by modifying the internal state of the system?

Modifying the internal state of a system involves changing data or parameters that determine the current behavior and condition of a program or component. In the context of Node.js, this could mean changing variable values, object properties, thread states, or cache, which affects the application's subsequent operation.

For example, if you have an object that stores server settings, changing these settings is a modification of the internal state:

const serverConfig = { port: 3000, mode: 'development' };

// Change the mode of operation
serverConfig.mode = 'production';

Such changes can influence the application's logic, request handling, and other processes. It is important to control these changes to avoid unpredictable behavior.