vue获取浏览器缩放比例

detectZoom() {
  var ratio = 0, 
  screen = window.screen, 
  ua = navigator.userAgent.toLowerCase();
  if (window.devicePixelRatio !== undefined) {
    ratio = window.devicePixelRatio;
  } else if (~ua.indexOf('msie')) {
    if (screen.deviceXDPI && screen.logicalXDPI) {
      ratio = screen.deviceXDPI / screen.logicalXDPI;
    }
  } else if (window.outerWidth !== undefined && window.innerWidth !== undefined) {
    ratio = window.outerWidth / window.innerWidth;
  }
  if (ratio) {
    ratio = Math.round(ratio * 100);
  }
  return ratio;
},