js获取页面缩放比例

//获取当前页面的缩放值
    function 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;
    }