<html>
<head>
<script>
function copyText()
{
document.getElementById("field2").value=document.getElementById("field1").value;
}
</script>
</head>
<body>
字段1: <input type="text" id="field1" value="Hello World!"><br>
字段2: <input type="text" id="field2">
<br><br>
<button ondblclick="copyText()">复制文本</button>
<p>在按钮双击时触发函数。函数将字段1的文字信息复制到字段2。</p>
</body>
</html>