How many types of nodejs events are there?

Node.js is a server-side JavaScript runtime built on an event-driven, non-blocking I/O model. It can be seen that events play a very important role in the development of Node.js. So, how many types of events are there in Node.js? This article will introduce you to various events in Node.js in detail.

In Node.js, events are also called triggers, which are triggered by the EventEmitter object. EventEmitter is a core module provided by Node.js. Its principle is that once the required event is triggered, Node.js will call all callback functions bound to this event. In Node.js, the triggering of events and the execution of callback functions are asynchronous, which means that Node.js does not wait for the completion of the event, but continues to perform subsequent operations. This is one of the very efficient mechanisms of Node.js.

The following will introduce you to the common event types in Node.js:

1. Connection event (connection)

The connection event is when a new client request arrives event triggered when. In Node.js, you can use the net.createServer() method to create a TCP server and then listen to the connection event. This event is triggered when a new client connects to this server.

2. Close event (close)

The close event is an event triggered when the server or client connection is closed. In Node.js, you can use the socket.on('close') method to bind this event, which is triggered when the server or client connection is closed.

3. Error event (error)

The error event is an event triggered when an error occurs. In Node.js, you can use the socket.on('error') method to bind this event, and this event will be triggered when an error occurs.

4. Data event (data)

Data event is an event triggered when data is received. In Node.js, you can use the socket.on('data') method to bind this event. This event will be triggered when data arrives.

5. End event (end)

The end event is an event triggered after the server or client has sent the data. In Node.js, you can use the socket.on('end') method to bind this event. This event will be triggered when the data is sent.

6. Timeout event (timeout)

The timeout event is an event triggered when the connection times out. In Node.js, you can use the socket.setTimeout() method to set the timeout. When the connection exceeds the set time without any response, this event will be triggered.

7. Writable event (drain)

Writable event is an event triggered when the data written to the buffer is consumed. In Node.js, you can use the socket.on('drain') method to bind this event. This event will be triggered when the buffer for writing data is cleared.

8. Upgrade event (upgrade)

The upgrade event is an event triggered during HTTP upgrade. In Node.js, you can use the http.createServer() method to create an HTTP server and then listen to the upgrade event. This event is fired when a request is upgraded to WebSockets or HTTP/2.

The above are the common event types in Node.js. In addition, Node.js has other event types, such as pipe, unpipe, finish, etc. Understanding the event types of Node.js is very important for Node.js development. By learning and mastering the event mechanism, it can help us better understand the core concepts and programming model of Node.js.

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