what is on and once in node

The on and once functions in Node.js are used for event handling. Here is an explanation for each step:

1. on: The on function is used to add a listener to an event. It takes two arguments: the event name and a callback function. The callback function is executed whenever the specified event is emitted. The on function allows multiple listeners to be attached to the same event.

2. once: The once function is similar to on, but it adds a one-time listener to an event. This means that the listener is automatically removed after it is executed once. It also takes two arguments: the event name and the callback function.

These functions are often used in Node.js to handle events such as HTTP requests, file system operations, and database queries. By attaching listeners to events, developers can write code that executes asynchronously, responding to events as they occur.