tlds2/src/checkDomain.js

Comprehensive list of TLDs and subdomain registrars

// Define arrays for allowed characters
const allowedAlphanum = [];
const allowedSpecial = [];

// Initialize the arrays with false for all ASCII characters
for (var i = 0; i < 256; i++) {
    allowedAlphanum[i] = false;
    allowedSpecial[i] = false;
}

// Set the ranges for alphanumeric characters (A-Z, a-z, 0-9)
for (var i = 65; i <= 90; i++) {
    allowedAlphanum[i] = true;
    allowedSpecial[i] = true;
}

for (var i = 97; i <= 122; i++) {
    allowedAlphanum[i] = true;
    allowedSpecial[i] = true;
}

for (var i = 48; i <= 57; i++) {
    allowedAlphanum[i] = true;
    allowedSpecial[i] = true;
}

// Set specific special characters (- and _)
allowedSpecial[45] = true;
allowedSpecial[95] = true;


/**
 * Checks if a string only contains allowed characters.
 * @param {string} str - The string to check.
 * @param {boolean[]} table - The table of allowed characters.
 * @returns {boolean} - Returns true if the string only contains allowed characters, false otherwise.
 */
function isIn(str, table) {
    for (var i = 0; i < str.length; i++) {
        var codeAscii = str.charCodeAt(i);
        if (!table[codeAscii]) {
            return false;
        }
    }
    return true;
}

/**
 * Checks if a string contains only allowed alphanumeric characters.
 * @param {string} str - The string to check.
 * @returns {boolean} - Returns true if the string only contains allowed alphanumeric characters, false otherwise.
 */
function isAlphanum(str) {
    return isIn(str, allowedAlphanum);
}

/**
 * Checks if a string contains only allowed characters for a basic email username.
 * @param {string} str - The string to check.
 * @returns {boolean} - Returns true if the string only contains allowed characters for a basic email username, false otherwise.
 */
function isEmailSpecial(str) {
    return isIn(str, allowedSpecial);
}

/**
 * Checks a domain name for validity.
 * @param {string} domain - The domain name to check.
 * @returns {object} - Returns an object with 'error' and 'punycode' properties.
 */
function checkDomain(domain) {
    const ret = { error: null, punycode: false }

    if (typeof domain !== 'string') {
        ret.error = 'Invalid domain'
        ret.info  = 'Domain must be a string'
        return(ret)
    }

    if (domain.length > 320) {
        ret.error = 'Invalid domain'
        ret.info = 'Domain is too long'
        return(ret)
    }

    // Check domain name
    const domainItems = domain.split(".")
    for (var item of domainItems) {
        if (item.length === 0) {
            ret.error = 'Invalid domain'
            ret.info = "Zero length label"
            return (ret)
        }

        if (item.length > 62) {
            ret.error = 'Invalid domain';
            ret.info = "Label length greater than 62";
            return (ret)
        }

        // Check if the first and last characters are alphanumeric
        const first = isAlphanum(item[0])
        const middle = isEmailSpecial(item)
        const last = isAlphanum(item[item.length - 1])
        if (first === false || last === false || middle === false) {
            ret.error = 'Invalid domain'
            ret.info = "Invalid label encoding"
            return (ret)
        }

        // Check for punycode encoding
        const punyCode = /(xn--)/
        if (item.match(punyCode))
            ret.punycode = true
    }

    return (ret)
}

module.exports = checkDomain