JS獲取頁面的縮放比例

正常值為100,如果放大到150%,則顯示150

//獲取當前頁面的縮放值
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;
}