语法：
onfocus="SomeJavaScriptCode"
onfocus 事件在对象获得焦点时发生。
支持该事件的 HTML 标签：
<a>, <acronym>, <address>, <area>, <b>, <bdo>, <big>, <blockquote>, <button>,
<caption>, <cite>, <dd>, <del>, <dfn>, <div>, <dl>, <dt>, <em>, <fieldset>,
<form>, <frame>, <frameset>, <h1> to <h6>, <hr>, <i>, <iframe>, <img>, <input>,
<ins>, <kbd>, <label>, <legend>, <li>, <object>, <ol>, <p>, <pre>, <q>,
<samp>, <select>, <small>, <span>, <strong>, <sub>, <sup>, <table>, <tbody>,
<td>, <textarea>, <tfoot>, <th>, <thead>, <tr>, <tt>, <ul>, <var>
支持该事件的 JavaScript 对象：
button, checkbox, fileUpload, layer, frame, password, radio, reset, select, submit,
text, textarea, window
例：
输入框获得焦点时，改变其背景色：
<span style="font-size:18px;"><html>
<head>
<script type="text/javascript">
function setStyle(id)
{
document.getElementById(id).style.background="yellow"
}
</script>
</head>
<body>
名称: <input type="text" onfocus="setStyle(this.id)" id="name" />
<br />
年龄: <input type="text" onfocus="setStyle(this.id)" id="age" />
</body>
</html></span>
时间： 2024-10-13 22:43:11