弹出对话框的六种写法：

$是Jquery中的顶级对象
$(function () {
            alert('aaa');
        });
        jQuery(function () {
            alert('bbb');
        });
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        $(document).ready(function () {
            alert('ccc');
        });
        jQuery(document).ready(function () {
            alert('dddd');
        });
---------------------------------------------
        $(window).load(function () {
            alert('eee');
        });
        jQuery(window).load(function () {
            alert('fff');
        });