☀【DOM对象 / jQuery对象】

jQuery对象和DOM对象 √
http://www.ituring.com.cn/article/38868
<!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="utf-8">
    <title></title>
</head>
<body>
    <ul>
        <li>item</li>
        <li>item</li>
    </ul>
    <script src="http://static01.baomihua.com/js/lib/jquery-1.4.4.min.js?t=20120926.js"></script>
    <script>
        var aElem = $('a')
        var liElem = $('li')

        console.log(aElem)
        console.log(aElem.length)
        console.log(aElem[0])
        console.log(liElem)
        console.log(liElem.length)
        console.log(liElem[0], liElem[1])

        aElem.click(function() {
        })
        if (aElem[0]) {
        }

        var aElem = document.getElementsByTagName('a')[0]
        var liElem = document.getElementsByTagName('li')[0]

        console.log(aElem)
        console.log(liElem)

        if (aElem) {
            aElem.onclick = function() {
            }
        }
        liElem.onclick = function() {
        }

        function getElem(elem) {
            return document.getElementsByTagName(elem)[0] || document.createElement(elem) // 这样处理不报错了，jQuery怎么处理？
        }
        getElem('a').onclick = function() {
        }
    </script>
</body>
</html>