js不能获取隐藏的div的宽度只能先显示后获取

var tipsWidth = $(".Loading").css("width").replace("px", "") //先获得 
var windowWidth = $(window).width(); 
$(".Loading").css({ "display": "block" }); //再显示 
$(".Loading").css({ "left": (windowWidth - tipsWidth) / 2 + "px" }); 
var tipsWidth = $(".Loadin