'use strict';

function isValid(id) {
    // Make sure we have a string
    id = '' + id;
    if (id.match(/^[\-\s+\d]+$/) === null) {
        return false;
    }
    // Remove all non digits
    id = id.replace(/\D/g, '')
    if (id.length !== 10 && id.length !== 12) {
        return false;
    }
    if (id.length === 12) {
        // Validate century prefix and reduce string that is to be validated to 10 digits
        // Other prefixes than these indicate that it is a company
        var prefix = parseInt(id.substring(0, 2));
        if (prefix < 18 || prefix > 20) {
            return false;
        }
        // Validate that year is not greater than current
        var currentYear = (new Date()).getFullYear();
        if (parseInt(id.substring(0, 4)) > currentYear) {
            return false;
        }
        id = id.substring(2);
    }
    var sum = 0;
    for (var i = 0; i < id.length; i++) {
        var value = parseInt(id.charAt(i));
        sum += getValidationValue(i, value);
    }
    return sum % 10 == 0;
}

function getValidationValue(index, baseValue) {
    if (index % 2 !== 0) {
        return baseValue;
    }
    var doubled = 2 * baseValue;
    if (doubled < 10) {
        return doubled;
    } else {
        return 1 + (doubled - 10);
    }
}

var toTest = [
    8209244113,
    "8209244113",
    "820924-4113",
    "820924+4113",
    "18820924-4113",
    "19820924-4113",
    "201302091077",
    " 82 09 24 - 4113",
    null,
    "",
    "8209244119",
    "AA09244113",
    "AA8209244113",
    "820924B4113",
    "17820924-4113",
    "20820924-4113",
    "201202091077",
    " 82 09 24 _ 4014"
];

toTest.forEach(function(value) {
    var ok = isValid(value);
    console.log(value + " is valid: " + (ok ? 'true' : 'false'));
})