TAZIO MIRANDOLA Web Applications Developer

tipical workflow:

git clean -f -d
git pull origin/master
npm install
gulp build
systemctl restart myapp

  typings search node
  typings install --save --global dt~node
  typings install --save --global dt~mocha-node
  npm install -g mocha

Async Architecture: notification/event driven

The node.js event loop: node.js platform works in one single process which handles the web requests. But all the IO operations and the other function calls are asynchronous in nature. They are "waked" by a callback listener from the node.js main process and they run each of the calls in different threads (Child Processes). In the main process, the node.js server call is never blocked as this process only delegates the IO tasks to the sub processes (worker threads).

REPL

nodejs

FileSystem operations

#!/usr/bin/env node
 
var fs = require('fs');
var qry = fs.existsSync('/etc/hosts');
var stat = fs.statSync('/etc/hosts');
var qry2 = stat.isFile();
 
fs.readFile(fs.realpathSync(filename), 'utf8', function (err,data) {
    if (err) {
        return console.log(err);
    }
    data;
});
 
fs.writeFile(filename, data, function (err) {
    if (err) return console.log(err);
    console.log('File writing done');
});

simple node program:

#!/usr/bin/env node
var s_date_time = new Date();
console.log('Stating: ' + s_date_time);
var i_counter = 0;
for (var $i_loop1 = 0; $i_loop1 < 10; $i_loop1++) {
   for (var $i_loop2 = 0; $i_loop2 < 32000; $i_loop2++) {
       for (var $i_loop3 = 0; $i_loop3 < 32000; $i_loop3++) {
           i_counter++;
           if (i_counter > 50) {
               i_counter = 0;
           }
       }
   }
}
var s_date_time_end = new Date();
console.log('End: ' + s_date_time_end + '\n');

CLI arguments

node nodecmd_test one two three

#!/usr/bin/env node
process.argv.forEach(function (val, index, array) {
  console.log(index + ': ' + val);
});

#!/usr/bin/env node
process.stdin.resume();
process.stdin.setEncoding('utf8');
var util = require('util');
process.stdin.on('data', function (text) {
    console.log('received data:', util.inspect(text));
    if (text === 'exit\\n') {
        complete();
    } else {
        invalidCommand();
    }
});
function complete() {
    console.log('There is nothing to do now.');
    process.exit();
}
function invalidCommand() {
    console.log('Please enter the valid command');
}

Modules loading

var http = require('http');
// loading user defined modules
var checkData = require('./validatorutil');

Module Definition

var checkEmail = function(value) {
   try {
      check(value).isEmail();
   } catch (e) {
      return e.message; //Invalid integer
   }
   return value;
};
module.exports.checkEmail = checkEmail;

download modules:

npm install <>

simple node web server:

#!/usr/bin/env node
var http = require("http");
var url = require("url");
function start_server(param){
    function onRequest(request, response) {
        response.writeHead(200, {"Content-type": "text/html"});
 
        response.write("<a>Smile!</a>");
 
        response.end();
    }
    http.createServer(onRequest).listen(8181, "127.0.0.1");
}
start_server(param);

binary data

var buffer = new Buffer('this is a good place to start');

var slice = new Buffer(10);

var startTarget = 0,start = 10,end = 20;

buffer.copy(slice, startTarget, start, end);
console.log(buf.toString());
console.log(buf.toString('base64'));
buffer.fill("0");
var json = JSON.stringify(buf);

Pub/sub

var util = require('util');
util.inherits(myEventEmitterClass, EventEmitter);
myEventEmitterClass.prototype.emittedMethod = function() {
    console.log('before the emittedMethod');
    this.emit('emittedevent');
    console.log('after the emittedMethod');
}
someObject.on('emittedevent', function() {
    console.log('The emittedevent is called');
});