为什么在使用jquery的firefox中放大和缩小功能不能正常工作?

这是我的代码:

$('#In').on('click', function () {
    if (navigator.userAgent.indexOf('Firefox') != -1 && parseFloat(navigator.userAgent.substring(navigator.userAgent.indexOf('Firefox') + 8)) >= 3.6) {//Firefox  
        var step = 0.02;
        currFFZoom += step;
        $('body').css('MozTransform', 'scale(' + currFFZoom + ')');
        save_zoom_level(currFFZoom);
    } else {
        var step = 2;
        currIEZoom += step;
        $('body').css('zoom', ' ' + currIEZoom + '%');
        save_zoom_level(currIEZoom);
    }
});

$('#Out').on('click', function () {
    if (navigator.userAgent.indexOf('Firefox') != -1 && parseFloat(navigator.userAgent.substring(navigator.userAgent.indexOf('Firefox') + 8)) >= 3.6) {//Firefox  
        var step = 0.02;
        currFFZoom -= step;
        $('body').css('MozTransform', 'scale(' + currFFZoom + ')');
        save_zoom_level(currFFZoom);

    } else {
        var step = 2;
        currIEZoom -= step;
        $('body').css('zoom', ' ' + currIEZoom + '%');
        save_zoom_level(currIEZoom);
    }
});

function zoomIn() { var element = document.getElementById("content"); element.classList.add("zoomIn"); } function zoomOut() { var element = document.getElementById("content"); element.classList.remove('zoomIn').add("zoomOut"); }