Javascript 使用jquery调整div大小失败

我想用jquery调整我的div“container”的大小，我想我知道该怎么做了。但不幸的是，ist不起作用。以下是我的简单代码：

var viewport = $( window ).height();
var container_height = viewport - 125;
alert("setting height to "+container_height);
$( "#container" ).height(container_height);
alert("height is now " + $( "#container" ).height());

第一个警报告诉我正确的高度，但第二个警报告诉我，它是空的

怎么了？

---

谢谢

这对我很管用，试试这个：

$(window).on('resize', function(){

    var viewport = $( window ).height();

    var container_height = viewport - 125;

    $( "#container" ).height(container_height);
});

它在这里起作用

JS

 $(window).on('resize', function () {
    var viewport = $(window).height();
    var container_height = viewport - 125;
    alert("setting height to " + container_height);
    $("#container").height(container_height);
    alert("height is now " + $("#container").height());

});

#container{

    width:200px;
    height:200px;
    background:Yellow;
}

 $(window).on('resize', function () {
    var viewport = $(window).height();
    var container_height = viewport - 125;
    alert("setting height to " + container_height);
    $("#container").height(container_height);
    alert("height is now " + $("#container").height());

});