function isNull(name, str) {
    if (trim(name.value) == "") {
        alert(str);
        name.focus();
        return true;
    }
    return false;
}

function trim(str) {
    var len;
    var i, j;
    len = str.length;
    i = 0;
    j = 0;
    while (j < len) {
        if (str.charAt(i) == " ")
            i++;
        else
            break;
        j++;
    }
    str = str.substr(i, len - i);
    len = str.length;
    i = len - 1;
    j = len - 1;
    while (j > 0) {
        if (str.charAt(i) == " ")
            i--;
        else
            break;
        j--;
    }
    str = str.substr(0, j + 1);
    return str;
}

function checkIdcard(idcard) {
    var area = { 11: "北京", 12: "天津", 13: "河北", 14: "山西", 15: "内蒙古", 21: "辽宁", 22: "吉林", 23: "黑龙江", 31: "上海", 32: "江苏", 33: "浙江", 34: "安徽", 35: "福建", 36: "江西", 37: "山东", 41: "河南", 42: "湖北", 43: "湖南", 44: "广东", 45: "广西", 46: "海南", 50: "重庆", 51: "四川", 52: "贵州", 53: "云南", 54: "西藏", 61: "陕西", 62: "甘肃", 63: "青海", 64: "宁夏", 65: "新疆", 71: "台湾", 81: "香港", 82: "澳门", 91: "国外" }

    var idcard, Y, JYM;
    var S, M;
    var idcard_array = new Array();
    idcard_array = idcard.split("");
    //地区检验
    if (area[parseInt(idcard.substr(0, 2))] == null) return 4;
    //身份号码位数及格式检验
    switch (idcard.length) {
        case 15:
            if ((parseInt(idcard.substr(6, 2)) + 1900) % 4 == 0 || ((parseInt(idcard.substr(6, 2)) + 1900) % 100 == 0 && (parseInt(idcard.substr(6, 2)) + 1900) % 4 == 0)) {
                ereg = /^[1-9][0-9]{5}[0-9]{2}((01|03|05|07|08|10|12)(0[1-9]|[1-2][0-9]|3[0-1])|(04|06|09|11)(0[1-9]|[1-2][0-9]|30)|02(0[1-9]|[1-2][0-9]))[0-9]{3}$/; //测试出生日期的合法性
            } else {
                ereg = /^[1-9][0-9]{5}[0-9]{2}((01|03|05|07|08|10|12)(0[1-9]|[1-2][0-9]|3[0-1])|(04|06|09|11)(0[1-9]|[1-2][0-9]|30)|02(0[1-9]|1[0-9]|2[0-8]))[0-9]{3}$/; //测试出生日期的合法性
            }
            if (ereg.test(idcard)) return 0;
            else return 2;
            break;
        case 18:
            //18位身份号码检测
            //出生日期的合法性检查 
            //闰年月日:((01|03|05|07|08|10|12)(0[1-9]|[1-2][0-9]|3[0-1])|(04|06|09|11)(0[1-9]|[1-2][0-9]|30)|02(0[1-9]|[1-2][0-9]))
            //平年月日:((01|03|05|07|08|10|12)(0[1-9]|[1-2][0-9]|3[0-1])|(04|06|09|11)(0[1-9]|[1-2][0-9]|30)|02(0[1-9]|1[0-9]|2[0-8]))
            if (parseInt(idcard.substr(6, 4)) % 4 == 0 || (parseInt(idcard.substr(6, 4)) % 100 == 0 && parseInt(idcard.substr(6, 4)) % 4 == 0)) {
                ereg = /^[1-9][0-9]{5}19[0-9]{2}((01|03|05|07|08|10|12)(0[1-9]|[1-2][0-9]|3[0-1])|(04|06|09|11)(0[1-9]|[1-2][0-9]|30)|02(0[1-9]|[1-2][0-9]))[0-9]{3}[0-9Xx]$/; //闰年出生日期的合法性正则表达式
            } else {
                ereg = /^[1-9][0-9]{5}19[0-9]{2}((01|03|05|07|08|10|12)(0[1-9]|[1-2][0-9]|3[0-1])|(04|06|09|11)(0[1-9]|[1-2][0-9]|30)|02(0[1-9]|1[0-9]|2[0-8]))[0-9]{3}[0-9Xx]$/; //平年出生日期的合法性正则表达式
            }
            if (ereg.test(idcard)) {//测试出生日期的合法性
                //计算校验位
                S = (parseInt(idcard_array[0]) + parseInt(idcard_array[10])) * 7
                    + (parseInt(idcard_array[1]) + parseInt(idcard_array[11])) * 9
                    + (parseInt(idcard_array[2]) + parseInt(idcard_array[12])) * 10
                    + (parseInt(idcard_array[3]) + parseInt(idcard_array[13])) * 5
                    + (parseInt(idcard_array[4]) + parseInt(idcard_array[14])) * 8
                    + (parseInt(idcard_array[5]) + parseInt(idcard_array[15])) * 4
                    + (parseInt(idcard_array[6]) + parseInt(idcard_array[16])) * 2
                    + parseInt(idcard_array[7]) * 1
                    + parseInt(idcard_array[8]) * 6
                    + parseInt(idcard_array[9]) * 3;
                Y = S % 11;
                M = "F";
                JYM = "10X98765432";
                M = JYM.substr(Y, 1); //判断校验位
                if (M == idcard_array[17]) return 0; //检测ID的校验位
                else return 3;
            }
            else return 2;
            break;
        default:
            return 1;
            break;
    }
}