How to detect the filetype of the stream in NodeJS.

gistfile1.js

var
  beginBuff,
  beginBuffStr;
  
// type detection
if (chunkNum === 0) {
  beginBuff = data.slice(0, 8);
  beginBuffStr = beginBuff.toString('hex', 0, beginBuff.length);
  
  // jpg
  if (beginBuffStr.indexOf('ffd8ffe0') > -1) {
    console.log('JPG');
  }
  
  // xml
  else if (beginBuffStr.indexOf('3c3f786d6c207665') > -1) {
    console.log('XML');
  }
  
  ...
}

chunkNum += 1;