Example using new Buffer.concat

loadpng.js

var http = require('http');

var request = http.request({method: 'get', host: 'images.google.com', port: 80, path: '/intl/en_ALL/images/logos/images_logo_lg.gif'}, function(response) {
  var data = [];
  
  response.on('data', function(chunk) {
    data.push(chunk);
  });
  
  response.on('end', function() {
    data = Buffer.concat(data, parseInt(response.headers['content-length']) || undefined);
    require('fs').writeFileSync('./test.gif', data, 'binary');
  });
});

request.end();