js 屏蔽鼠标右键(鼠标键值与contestmenu)

<script language="javascript">
function blockright(oEvent) {
var oDiv = document.getElementById("display");
if (window.event) oEvent = window.event; //处理兼容性，获得事件对象
if (oEvent.button == 2)
alert("不能使用");
}  // www.osxue.com
window.onload = function() { 
document.onmousedown = blockright;
}
</script>
<div> 
<textarea rows="4" cols="50" id="textin">
</textarea>
<p id="display"></p>
</div>

function blockright(oEvent) { 
if (window.event) {
oEvent = window.event; //处理兼容性，获得事件对象
oEvent.returnValue = false;
}