devjam-server.js

var express = require('express'), // 4.x
    bodyParser = require('body-parser'), // express 4.x requires this
    yql = require('yql'),
    urlparse = require('url');

// Set up Express environment and enable it to read and write JSON bodies
var app = express();
app.use(bodyParser.json()); // for parsing application/json

// Generic Send Error Function
function sendError(res, code, msg) {
  var o = { 'error': msg };
  res.writeHead(code, {'Content-Type': 'application/json'});
  res.end(JSON.stringify(o));
}

// The API starts here
// GET /
app.get('/', function(req, res) {
  var rootTemplate = {
        'weather' : { 'href' : '/forecast' }
      };
  res.header('Content-Type', 'application/json')
    .status(200)
    .send(JSON.stringify(rootTemplate));
});

// GET /forecast
app.get('/forecast', function(req, res) {
  try {
    // parse the url and check for zipcode
    var parsed = urlparse.parse(req.url, true);
    if (!parsed.query.zipcode) {
      sendError(res, 400, 'Missing query parameter "zipcode"');
    } 
    else {
      // create the query per YQL module documentation & then execute the query
      var forecastQuery = 'SELECT * FROM weather.forecast WHERE (location = ' + 
        parsed.query.zipcode + ')';
      var query = new yql(forecastQuery);

      // execute the query and create/send the final response in the
      // anonymous callback function
      query.exec(function(err, data) {
        var finalResponse = {
              location : data.query.results.channel.location,
              units : data.query.results.channel.units,
              condition : data.query.results.channel.item.condition,
              forecast : data.query.results.channel.item.forecast
            };
        res.header('Content-Type', 'application/json')
          .status(200)
          .send(JSON.stringify(finalResponse));
      });
    }
  } 
  catch(e) {
    sendError(res, 500, "Internal Server Error - " + e.message);
  }
});

// all other requests
app.all(/^\/.*/, function(request, response) {
  response.header('Content-Type', 'application/json')
    .status(404)
    .send('{ "message" : "This is not the server you\'re looking for." }\n');
});

// start the server
app.listen(process.env.PORT || 9000, function() {
  console.log('The server is running!');
});