一個完整校驗身份證

/**
 * 校驗身份證號合法性
 */
function checkIdNumberValid(tex){
    var tip = '輸入的身份證號有誤，請檢查後重新輸入！';
    var num = tex.value;
    num = num.toUpperCase();

    var len, re;
    len = num.length;
    if(len == 0) return true;

    //身份證號碼為15位或者18位，15位時全為數字，18位前17位為數字，最後一位是校驗位，可能為數字或字元X。    
    if (!(/(^\d{15}$)|(^\d{17}([0-9]|X)$)/.test(num))){
        alert(tip);
        tex.focus();
        return false;
    }

    //驗證前兩位地區是否有效 
    var aCity= {11:"北京",12:"天津",13:"河北",14:"山西",15:"內蒙古",21:"遼寧",22:"吉林",23:"黑龍江 ",31:"上海",
                32:"江蘇",33:"浙江",34:"安徽",35:"福建",36:"江西",37:"山東",41:"河南",42:"湖北 ",43:"湖南",
                44:"廣東",45:"廣西",46:"海南",50:"重慶",51:"四川",52:"貴州",53:"雲南",54:"西藏 ",61:"陝西",
                62:"甘肅",63:"青海",64:"寧夏",65:"新疆",71:"臺灣",81:"香港",82:"澳門",91:"國外 "}
    if(aCity[parseInt(num.substr(0,2))] == null){
        alert(tip);
        tex.focus();
        return false;
    }

    //當身份證為15位時的驗證出生日期。 
    if (len == 15){
        re = new RegExp(/^(\d{6})(\d{2})(\d{2})(\d{2})(\d{3})$/);
        var arrSplit = num.match(re);

        //檢查生日日期是否正確  
        var dtmBirth = new Date('19' + arrSplit[2] + '/' + arrSplit[3] + '/' + arrSplit[4]);
        var bGoodDay;
        bGoodDay = (dtmBirth.getYear() == Number(arrSplit[2])) && ((dtmBirth.getMonth() + 1) == Number(arrSplit[3])) && (dtmBirth.getDate() == Number(arrSplit[4]));  
        if (!bGoodDay){
            alert(tip);
            tex.focus();
            return false;
        }
    }
    
    //當身份證號為18位時，校驗出生日期和校驗位。 
    if (len == 18){
        re = new RegExp(/^(\d{6})(\d{4})(\d{2})(\d{2})(\d{3})([0-9]|X)$/);
        var arrSplit = num.match(re);
        //檢查生日日期是否正確  
        var dtmBirth = new Date(arrSplit[2] + "/" + arrSplit[3] + "/" + arrSplit[4]);
        var bGoodDay;
        bGoodDay = (dtmBirth.getFullYear() == Number(arrSplit[2])) && ((dtmBirth.getMonth() + 1) == Number(arrSplit[3])) && (dtmBirth.getDate() == Number(arrSplit[4]));  
        if (!bGoodDay){
            alert(tip);
            tex.focus();
            return false;
        }
        else{
            //檢驗18位身份證的校驗碼是否正確。 
            //校驗位按照ISO 7064:1983.MOD 11-2的規定生成，X可以認為是數字10。 
            var valnum;
            var arrInt = new Array(7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2);
            var arrCh = new Array('1', '0', 'X', '9', '8', '7', '6', '5', '4', '3', '2');
            var nTemp = 0, i;
            for(i = 0; i < 17; i ++){
                nTemp += num.substr(i, 1) * arrInt[i];
            }
            valnum = arrCh[nTemp % 11];
            if (valnum != num.substr(17, 1)){
                alert(tip);
                tex.focus();
                return false;
            }
        }
    }
    return true;
}