function fun() {

        var realname = document.getElementById("realname");

        var telephone = document.getElementById("telephone");

        var email = document.getElementById("email");

        // 邮箱格式正则表达式

        var emailPattern =/^([a-zA-Z0-9_-])+@([a-zA-Z0-9_-])+(.[a-zA-Z0-9_-])+/;

        // 手机号格式正则表达式

        var phonePattern = /^(((13[0-9]{1})|159|153)+\d{8})$/;

        if (realname.value == ""){

            alert("姓名不能为空！");

            realname.focus();

            return false;

        }

        if (telephone.value == ""){

            alert("手机不能为空！");

            telephone.focus();

            return false;

        }else if(!phonePattern.test(telephone.value)){

            alert("手机号格式不正确！");

            telephone.focus();

            return false;

        }

        if (email.value == ""){

            alert("邮箱不能为空！");

            email.focus();

            return false;

        }else if(!emailPattern.test(email.value)){

            alert("邮箱格式不正确！");

            email.focus();

            return false;

        }

        return true;

    }