Promise Example

promiseExample.js

var Promise = require('bluebird');  
var fs = require('fs');  
Promise.promisifyAll(fs);
var myFile = '/tmp/test';  
fs.readFileAsync(myFile, 'utf8').then(function(txt) {  
    txt = txt + '\nAppended something!';
    fs.writeFile(myFile, txt);
}).then(function() {
    console.log('Appended text!');
}).catch(function(err) {
    console.log(err);
});