js禁止右键、选择、复制等操作的代码

<script type="text/javascript">
//禁用右键、选择、复制等
    document.oncontextmenu=function(){return false};
    document.ondragstart=function(){return false};
    document.onselectstart =function(){return false};
    document.onselect=function(){document.selection.empty();};
    document.oncopy=function(){document.selection.empty();};
    document.onbeforecopy=function(){return false};
    document.onmouseup=function(){document.selection.empty();};
</script>