JS验证身份证号码正确性

function checkIdcard(idcard) {
    var Errors = new Array(
        "验证通过!",
        "请输入18位身份证号!",
        "身份证号码出生日期超出范围或含有非法字符!",
        "身份证号码校验错误!",
        "身份证地区非法!"
    );
    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 Errors[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 Errors[0];
         else return Errors[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|20)[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]$/; //闰年出生日期的合法性正则表达式 
            } else {
                ereg = /^[1-9][0-9]{5}(19|20)[0-9]{2}((01|03|05|07|08|10|12)(0[1-9]|[1-2][0-9]|3[0-1])|(04|06|09|11)(0[1-9]|[1-2][0-9]|30)|02(0[1-9]|1[0-9]|2[0-8]))[0-9]{3}[0-9Xx]$/; //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 Errors[0]; //检测ID的校验位 
                else return Errors[3];
            }
            else return Errors[2];
            break;
        default:
            return Errors[1];
            break;
    }
}