nanotiming/index.js

var assert = require('assert')

module.exports = Nanotiming

function Nanotiming (name) {
  if (!(this instanceof Nanotiming)) return new Nanotiming(name)
  assert.equal(typeof name, 'string', 'Nanotiming: name should be type string')
  this._name = name
  this._enabled = typeof window !== 'undefined' &&
    window.performance && window.performance.mark
}

Nanotiming.prototype.start = function (partial) {
  if (!this._enabled) return
  var name = partial ? this._name + '/' + partial : this._name
  var uuid = this._uuid()
  window.performance.mark(name + '-start-' + uuid)
  return uuid
}

Nanotiming.prototype.end = function (uuid, partial) {
  if (!this._enabled) return

  assert.equal(typeof uuid, 'string', 'Nanotiming.end: uuid should be type string')

  var name = partial ? this._name + '/' + partial : this._name
  var endName = name + '-end-' + uuid
  var startName = name + '-start-' + uuid
  window.performance.mark(endName)
  if (window.requestIdleCallback) {
    window.requestIdleCallback(function () {
      window.performance.measure(name, startName, endName)
    })
  } else {
    window.performance.measure(name, startName, endName)
  }
}

Nanotiming.prototype._uuid = function () {
  return window.performance.now() % 9e6
}