part1_basics_02.md

Making an HTTP GET request

var http = require('http');

req = http.get('http://nodejs.org/api', onGet)
  .on('error', function(e) {
    console.log('problem with request: ' + e.message);
   });

function onGet(res) {
  res.on('data', function(chunk) {
    console.log('data:' + chunk);
  });
}

http.get(options, callback)

Convenience method for doing a GET request.

• options - a uri or a hash specfying params like host, method, headers, etc.
• res - the response.
• both req and res expose events. (http://nodejs.org/api/http.html#http_http_get_options_callback)
• data is called when a chunk of data is received
• error is called if any error error occurs whether DNS resolution, TCP level errors, or actual HTTP errors.

Making an HTTP POST request

var http=require('http');
var options = {
  hostname: 'www.google.com',
  port: 80,
  path: '/upload',
  method: 'POST'
};

var req = http.request(options, function(res) {
  console.log('STATUS: ' + res.statusCode);
  console.log('HEADERS: ' + JSON.stringify(res.headers));
  res.setEncoding('utf8');
  res.on('data', function (chunk) {
    console.log('BODY: ' + chunk);
  });
});

req.on('error', function(e) {
  console.log('problem with request: ' + e.message);
});

// write data to request body
req.write('data\n');
req.write('data\n');
req.end();

http.request(options, callback)

• make any type of http request
• options - a hash contain all the request information i.e. URI components, HTTP method, headers etc.
• http.get calls to http.request

Event emitters

• Many objects in node emit events, they are called Emitters
• Emitters are used for notifications vs callbacks which ae used for completion of executing async code.
• To add a listener use the on() method
• To remove listeners to an event use the removeListener method

req.on('error', function(e) {
  console.log('problem with request: ' + e.message);
});

Authoring emitters

• Derive from EventEmitter
• call emit to raise events.
• can be any number of args.

var util = require("util");
var events = require("events");

function MyStream() {
    events.EventEmitter.call(this);
}

util.inherits(MyStream, events.EventEmitter);

MyStream.prototype.write = function(data) {
    this.emit("data", data);
}

//consume
var obj = new MyStream();
obj.on('data', function(data) {
  console.log(data);
});

obj.write("hello");