判断是否移动设备

function isMobile() {
  if (typeof this._isMobile === "boolean") {
    return this._isMobile;
  }
  var screenWidth = this.getScreenWidth();
  var fixViewPortsExperiment =
    rendererModel.runningExperiments.FixViewport ||
    rendererModel.runningExperiments.fixviewport;
  var fixViewPortsExperimentRunning =
    fixViewPortsExperiment && fixViewPortsExperiment.toLowerCase() === "new";
  if (!fixViewPortsExperiment) {
    if (!this.isAppleMobileDevice()) {
      screenWidth = screenWidth / window.devicePixelRatio;
    }
  }
  var isMobileScreenSize = screenWidth < 600;
  var isMobileUserAgent = false;
  this._isMobile = isMobileScreenSize && this.isTouchScreen();
  return this._isMobile;
}