js判断回车，区分IE，火狐，谷歌

if(document.addEventListener){//如果是Firefox
            document.addEventListener("keypress",fireFoxHandler, true);
        }else{
            document.attachEvent("onkeypress",ieHandler);
        }
        function fireFoxHandler(evt){
            if(evt.keyCode==13){
                com_search();
            }
        }
        function ieHandler(evt){
            if(evt.keyCode==13){
                com_search();
            }
        }