js屏蔽各功能键

function doucment.oncontextmenu() {
event.returnValue = false;
}//屏蔽鼠标右键

function window.onhelp() {
return false;
}//屏蔽F1帮助

function document.onkeydown() {

if ( (window.event.altkey) &&         (window.event.keyCode == 37) ||   //屏蔽Alt + 左方向键        (window.event.keyCode == 39)) {   //屏蔽Alt + 右方向键    event.keyCode = 0;    event.returnValue = false;}if (    (event.keyCode == 116) || //屏蔽F5刷新键    (event.ctrlKey && event.keyCode == 82) //屏蔽Ctrl+R    ) {    event.keyCode = 0;    event.returnValue = false;}

}