A code snippet used to understand Buffer in CommonJS:

var fs = require('fs');

var rs = fs.createReadStream('test.cpp');
var buffers = [];
var nread = 0;

rs.on('data', function (chunk) {
  // collect all buffer in the read stream to arr
  buffers.push(chunk);
  nread += chunk.length;
});

rs.on('end', function () {
  var buffer = null;
  switch (buffers.length) {
    case 0:
      buffer = new Buffer(0);
      break;
    case 1:
      buffer = buffers[0];
      break;
    default:
      buffer = new Buffer(nread);
      //  the code below will join the buffer into new buffer
      //  .copy method is to copy a buffer to a new buffer at target place
      //  and after join the buffers, we can use .toString to convert it to str, default character set is utf-8
      for (var i = 0, pos = 0, l = buffers.length; i < l; i ++) {
        var chunk = buffers[i];
        chunk.copy(buffer, pos);
        pos += chunk.length;
      }
      break;
  }
  console.log(buffer.toString());
});