jQuery plugin : Taiwanese ID Checker 身分證字號檢查器

/*
    Program: Taiwanese ID Checker
    Author: Austin, Cheng-Chun Chang
    Blog: http://austinccc.blogspot.com
*/
jQuery.fn.checkId = function(){
    var moduleCnt = 10;
    var inputId = $.trim($(this).val()).toUpperCase();
    if(inputId.length != moduleCnt){ //If the length is not 10, return false
        return false;
    }else{
        var str = new Array(moduleCnt);
        switch(inputId.substring(0,1)){
            case 'A':
                str[0] = "1";
                str[1] = "0";
                break;
            case 'B':
                str[0] = "1";
                str[1] = "1";
                break;
            case 'C':
                str[0] = "1";
                str[1] = "2";
                break;
            case 'D':
                str[0] = "1";
                str[1] = "3";
                break;
            case 'E':
                str[0] = "1";
                str[1] = "4";
                break;
            case 'F':
                str[0] = "1";
                str[1] = "5";
                break;
            case 'G':
                str[0] = "1";
                str[1] = "6";
                break;
            case 'H':
                str[0] = "1";
                str[1] = "7";
                break;
            case 'I':
                str[0] = "3";
                str[1] = "4";
                break;
            case 'J':
                str[0] = "1";
                str[1] = "8";
                break;
            case 'K':
                str[0] = "1";
                str[1] = "9";
                break;
            case 'L':
                str[0] = "2";
                str[1] = "0";
                break;
            case 'M':
                str[0] = "2";
                str[1] = "1";
                break;
            case 'N':
                str[0] = "2";
                str[1] = "2";
                break;
            case 'O':
                str[0] = "3";
                str[1] = "5";
                break;
            case 'P':
                str[0] = "2";
                str[1] = "3";
                break;
            case 'Q':
                str[0] = "2";
                str[1] = "4";
                break;
            case 'R':
                str[0] = "2";
                str[1] = "5";
                break;
            case 'S':
                str[0] = "2";
                str[1] = "6";
                break;
            case 'T':
                str[0] = "2";
                str[1] = "7";
                break;
            case 'U':
                str[0] = "2";
                str[1] = "8";
                break;
            case 'V':
                str[0] = "2";
                str[1] = "9";
                break;
            case 'W':
                str[0] = "3";
                str[1] = "2";
                break;
            case 'X':
                str[0] = "3";
                str[1] = "0";
                break;
            case 'Y':
                str[0] = "3";
                str[1] = "1";
                break;
            case 'Z':
                str[0] = "3";
                str[1] = "3";
                break;
            default:
                //not characters, return false
                return false;
        }
        for(var i = 2; i < moduleCnt; i++){
            str[i] = inputId.substring(i-1,i);
        }
        var sum = parseInt(str[0]) * 1;
        for(var i = 9; i > 0; i--){
            sum = sum + (i * parseInt(str[moduleCnt - i]));
        }
        if((moduleCnt - (sum % moduleCnt)) == parseInt(inputId.substring(moduleCnt-1,moduleCnt)) || 
                (sum % moduleCnt) == parseInt(inputId.substring(moduleCnt - 1, moduleCnt))){
            return true;
        }else{
            return false;
        }
    }
}

How to use:

    $(document).ready(function(){
        $("#hi").click(function(){
            if($("#custId").checkId()){
                alert("ID is correct!!");
            }else{
                alert("ID is NOT Correct!!");
            }
        });
    });

If you would like to understand the rule, you could visit
身份證字號規則