Nodejs has a very complete event handling process
Every time we use a computer to open or close a file, it is an event
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var fs = require(‘fs’);
var rs =
fs.createReadStream(‘./demofile.txt’);
rs.on(‘open’, function () {
console.log(‘The file is open’);
});
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For example, the net.Server object triggers an event whenever there is a new connection; fs.ReadStream triggers an event when a file is opened; stream objects trigger events when data becomes readable
The createReadStream method is often used to open large text files and create a data stream for a read operation. A so-called large text file means a text file that is so large that the read buffer cannot hold it all, so it has to be sent in several batches. Each batch triggers a data event, and when the sending is finished, it triggers an end event.
Nodejs has a dedicated model for event handling
First, import the events module
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var events = require(‘events’);
var eventEmitter = new events.EventEmitter();
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EventEmitter Object
You can define the events to be triggered yourself, for example
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var events = require(‘events’);
var eventEmitter = new events.EventEmitter();
//Create an event handler:
var myEventHandler = function () {
console.log(‘I hear a scream!’);
}
//Assign the event handler to an event:
eventEmitter.on(‘scream’, myEventHandler);
//Fire the ‘scream’ event:
eventEmitter.emit(‘scream’);
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