popupVisible(newValue) {
  if (newValue) {
    document.body.style.position = 'fixed';
    document.body.style.width = '100%';
    document.body.style.height = '100%';
  }
  else {
    document.body.style.position = 'static';
    document.body.style.height = 'auto';
  }
},

popupVisible(newValue) {
  if (newValue) {
    document.body.style.position = 'fixed';
    document.body.style.width = '100%';
    document.body.style.height = '100%';
    this.top = window.scrollY;
  }
  else {
    document.body.style.position = 'static';
    document.body.style.height = 'auto';
    window.scrollTo(0, this.top);
  }
}

// 动态设置背景图的高度为浏览器可视区域高度
// 首先在Virtual DOM渲染数据时，设置下背景图的高度．
  this.bodyHeight = `${document.documentElement.clientHeight}`;
// 然后监听window的resize事件．在浏览器窗口变化时再设置下背景图高度．
 window.onresize = function temp() {
 var bodyHeight = `${document.documentElement.clientHeight}`;
 that.bodyHeight = bodyHeight;
 };