RSSHub/lib/utils/cf-email.js

/**
 * The alogrithm is well-explained in https://andrewlock.net/simple-obfuscation-of-email-addresses-using-javascript/
 */
module.exports = {
    // eslint-disable-next-line lines-around-comment
    /**
     * Returns decoded email address using CloudFlare's email address obfuscation.
     * @param {String} encoded - encoded email, (`cfemail` attribute in `__cf_email__` tag)
     * @returns decoded email address
     */
    decodeCFEmail: (encoded) => {
        const parseHex = (string, position) => parseInt(string.substr(position, 2), 16);
        let decoded = '';
        const key = parseHex(encoded, 0);
        for (let position = 2; position < encoded.length; position += 2) {
            const byte = parseHex(encoded, position) ^ key;
            decoded += String.fromCharCode(byte);
        }
        return decoded;
    },

    /**
     * Returns CloudFlare protected email address.
     * @param {String} email - email in plaintext
     * @returns obfuscated email
     */
    encodeCFEmail: (email) => {
        const key = Math.floor(Math.random() * 256);
        let encoded = ('0' + key.toString(16)).slice(-2);
        for (let position = 0; position < email.length; position++) {
            const byte = email.charCodeAt(position) ^ key;
            encoded += ('0' + byte.toString(16)).slice(-2);
        }
        return encoded;
    },
};