JS 身份证号码验证
以下代码是从腾讯团购网站上提取的身份证号码验证，仅为学习参考之用。
（通过 http://jsbeautifier.org/ 进行代码格式化）

function checkIdcard(elem) {    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 = elem.toUpperCase();    var Y, JYM;    var S, M;    var idcard_array = new Array();    idcard_array = idcard.split("");    if (area[parseInt(idcard.substr(0, 2))] == null) {        return false;    }    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}$/;        } else {            ereg = /^[1-9][0-9]{5}[0-9]{2}((01|03|05|07|08|10|12)(0[1-9]|[1-2][0-9]|3[0-1])|(04|06|09|11)(0[1-9]|[1-2][0-9]|30)|02(0[1-9]|1[0-9]|2[0-8]))[0-9]{3}$/;        }        if (ereg.test(idcard)) {            return true;        } else {            return false;        }        break;    case 18:        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]$/;        } else {            ereg = /^[1-9][0-9]{5}(19|20)[0-9]{2}((01|03|05|07|08|10|12)(0[1-9]|[1-2][0-9]|3[0-1])|(04|06|09|11)(0[1-9]|[1-2][0-9]|30)|02(0[1-9]|1[0-9]|2[0-8]))[0-9]{3}[0-9Xx]$/;        }        if (ereg.test(idcard)) {            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);            if (M == idcard_array[17]) {                return true;            } else {                return false;            }        } else {            return false;        };        break;    default:        {            return false;        }        break;    }    return true;}