function msr (origFunc) {
  origFunc = origFunc || this
  function wrappedFunc () {
    var args = arguments
    var origCb = arguments[args.length - 1]
    var startTime = Date.now()
    function wrapCb () {
      var endTime = Date.now()
      console.log('### Duration in ms', endTime - startTime, 'for', origFunc.name)
      return origCb.apply(this, arguments)
    }
    args[args.length - 1] = wrapCb
    var retVal = origFunc.apply(this, args)
    // var syncCallTime = Date.now()
    return retVal
  }
  return wrappedFunc
}
Function.prototype.msr = msr

//usage
// to measure
fs.writeFile('a1.txt', function (err, data) { /* read data */ })
// change it to
fs.writeFile.msr()('a1.txt', function (err, data) { /* read data */ })
// or
msr(fs.writeFile)('a1.txt', function (err, data) { /* read data */ })