document-ready-promise/document-ready-promise.js

A simple ES2015 Promise-based "document ready" event handler.

(function (document, promise) {
  if (typeof module !== 'undefined') module.exports = promise
  else document.ready = promise
})(window.document, function (chainVal) {
  'use strict'

  var d = document,
      w = window,
      loaded = /^loaded|^i|^c/.test(d.readyState),
      DOMContentLoaded = 'DOMContentLoaded',
      load = 'load'

  return new Promise(function (resolve) {
    if (loaded) return resolve(chainVal)

    function onReady () {
      resolve(chainVal)
      d.removeEventListener(DOMContentLoaded, onReady)
      w.removeEventListener(load, onReady)
    }

    d.addEventListener(DOMContentLoaded, onReady)
    w.addEventListener(load, onReady)
  })
})