javascript 正在加载中，请稍后效果实现

/*蒙版*/
.loading-mask {
    width: 100%;
    height: 100%;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: #fff;
    opacity: 0.3;
    filter: alpha(opacity = 30);
    z-index: 10000;
}

/*动态加载图片*/
.loading {
position: fixed;
top: 0;
left: 0;
width: 100%;
height: 100%;
background: url(loading.gif) 50% 50% no-repeat;
z-index: 10010;
}

//增加body遮罩
function maskElement(maskLevel) {
    if (!maskLevel) {
        maskLevel = '0';
    }

    if ($(".mask-level-" + maskLevel).length == 0) {
        $("body").append('<div class="loading-mask mask-level-' + maskLevel + '"></div>');
    }
}

//取消body遮罩
function unmaskElement(maskLevel) {
    if (!maskLevel) {
        maskLevel = '0';
    }
    $(".mask-level-" + maskLevel).remove();
}

function loadingShow(isMask) {
    if (isMask) {
        common.maskElement("0");
    }
    if ($(".loading").length == 0) {
        $("body").append('<div class="loading"></div>');
    }
}

function loadingHide() {
    unmaskElement("0");
    $(".loading").remove();
}