events_example.js

const fs = require("fs");
let data = '';

// Create a readable stream
let readerStream = fs.createReadStream('input.txt', {encoding: 'UTF8'});

// Handle stream events --> data, end, and error
// Note that file read/write involves I/O operations.
// And it is thus, an asynchronous task.

// 'data' event signifies that a chunk of data is read from the file
readerStream.on('data', function(chunk) {
    data += chunk;
});

// 'end' event signifies that the end of file has been reached
readerStream.on('end',function() {
    console.log(data);
});

// 'error' event signifies that some error occured while reading file
readerStream.on('error', function(err) {
    console.log(err.stack);
});