<script>
document.onmousedown = function(){return false;}
document.oncontextmenu = function(){window.status="oncontextmenu"}
</script>先onmousedown,再oncontextmenu
document.onmousedown = function(){return false;}
document.oncontextmenu = function(){window.status="oncontextmenu"}
</script>先onmousedown,再oncontextmenu
event.button