value 属性可设置或返回显示在按钮上的文本。
buttonObject.value=sometext
<html>
<head>
<script type="text/javascript">
function alertValue()
{
alert(document.getElementById("myButton").value)
}
</script>
</head>
<body>
<form>
<input type="button" value="Click me!" id="myButton"
onclick="alertValue()" />
</form>
</body>
</html>