Node Js is a asynchronous event-driven runtime. Node Js can perform tasks asynchronously, i.e. without waiting for a task to be executed, it can move further. Node Js has a built-in module named “events”. “events” module has EventEmitter() class. With the instance of EventEmitter() class we can handle multiple events. Every event takes a function as a callback, whenever the event occurs, the callback function get called. Every event is a named event. The callback functions are executed in the order, in which they are registered.
Example :
eventEmitter.on() and eventEmitter.addListener() works in similar way, but the eventEmitter.once() only executes the listener function once, after that it removes the callback function from the listener list.
