JS+按钮事件验证

//选中按钮
            function checkAll() {
                for (var i = 0; i < document.getElementsByName("selectFlag").length; i++) {
                    document.getElementsByName("selectFlag")[i].checked = document.getElementById("ifAll").checked;
                }
            }
            //添加
            function addStudent(){
                window.self.location ="add.do";
            }
            //删除
            function deleteStudent(){
                var flag = false;
                for (var i = 0; i < document.getElementsByName("selectFlag").length; i++) {
                    //                    alert(document.getElementsByName("selectFlag")[i].checked);
                    if (document.getElementsByName("selectFlag")[i].checked) {
                        flag = true;
                    }
                }
                if (!flag) {
                    alert("请选择需要删除的用户！");
                    return;
                }
                if (window.confirm("确认删除吗？")) {
                    //提交
                    document.getElementById("myform2").method = "post";
                    document.getElementById("myform2").action = "delete.do";
                    document.getElementById("myform2").submit();
                }
            }
            //更新
            function ModStudent(){
                var count = 0;
                var j = 0;
                for (var i=0; i<document.getElementsByName("selectFlag").length; i++) {
                    if (document.getElementsByName("selectFlag")[i].checked) {
                        j = i;
                        count ++;
                    }
                }
                if (count == 0) {
                    alert("请选择需要修改的用户");
                    return
                }
                if (count>1) {
                    alert("一次只能修改一个用户!");
                    return
                }
                if (count == 1) {
                    /*
                     *假如客户选择了多个用户,控制好传递的id值.
                     **/
                    window.self.location = "findByUserId.do?stdId="+document.getElementsByName("selectFlag")[j].value;
                }
            }