<body>
<script type="text/javascript">
function buttonchange() {
document.getElementById("but").value = "已改变";
}
</script>
<input type="button" id="but" value="改变" onclick="buttonchange()" />
</body>
<body>
<script type="text/javascript">
function buttonchange() {
document.getElementById("but").value = "已改变";
}
</script>
<input type="button" id="but" value="改变" onclick="buttonchange()" />
</body>