;(function () {
  if (typeof window.WeakRef !== 'undefined') {
    return
  }

  window.WeakRef = (function (weakMap) {
    function WeakRef(target) {
      weakMap.set(this, target)
    }
    WeakRef.prototype.deref = function () {
      return weakMap.get(this)
    }

    return WeakRef
  })(new WeakMap())
})()