zone-run-inside.ts

var currentZoneFrame = {zone: root, parent: null};
class Zone {
  static get current() {
    return currentZoneFrame.zone; 
  }

  run(callback, applyThis, applyArgs) {
    _currentZoneFrame = {parent: _currentZoneFrame, zone: this};
    try {
      return callback.apply(applyThis, applyArgs);
    } finally {
      _currentZoneFrame = _currentZoneFrame.parent;
    } 
  }
}

var _currentZoneFrame = {zone: root, parent: null};
class Zone {
  static get current() {
    return _currentZoneFrame.zone; 
  }

  run(callback, applyThis, applyArgs) {
    _currentZoneFrame = {parent: _currentZoneFrame, zone: this};
    try {
      return callback.apply(applyThis, applyArgs);
    } finally {
      _currentZoneFrame = _currentZoneFrame.parent;
    } 
  }
}

The global variable must begin with an underscore.