index.js

var fs = require('fs'),
    path = require('path');

var dataFile = 'country_names_and_code_elements_txt',
    fromCode = {},
    fromName = {};

// Read data from ISO's file
fs.readFileSync(path.join(__dirname, dataFile), 'ascii')
    .split('\r\n')
    .forEach(function(line) {
        var row = line.split(';'),
            code = row.pop(),
            nameParts = row.pop(),
            name = '';

        if (!code || !nameParts) {
            return;
        }

        // Make sure we know both "Iran" and "Iran, Islamic Republic of"
        nameParts.split(/,\s+/).forEach(function(namePart) {
            name += namePart;
            fromCode[code.toUpperCase()] = name;
            fromName[name.toUpperCase()] = code;
            name += ', ';
        });
});

// Register a number of name variants and special cases
fromName['KOSOVO'] = fromName['REPUBLIC OF KOSOVO'] = fromName['KOSOVO AND METOHIJA'] = 'XK';
fromName['MACEDONIA (FYROM)'] = fromName['MACEDONIA'];
fromName['SYRIA'] = fromName['SYRIAN ARAB REPUBLIC'];
fromName['REPUBLIC OF THE PHILIPPINES'] = fromName['PHILIPPINES'];
fromName['UNITED STATES OF AMERICA'] = fromName['USA'] = fromName['UNITED STATES'];
fromName['RUSSIA'] = fromName['RUSSIAN FEDERATION'];
fromName['SOUTH KOREA'] = fromName['KOREA, REPUBLIC OF'];
fromName['THE NETHERLANDS'] = fromName['NETHERLANDS'];
fromName['SÃO TOMÉ AND PRÍNCIPE'] = fromName['SAO TOME AND PRINCIPE'];

/**
 * Get a country code for a country name. Case-insensitive.
 *
 * Examples:
 *
 *   // Returns 'CH'
 *   countrynames.getCode('Switzerland')
 *   // Returns 'BB'
 *   countrynames.getCode('BarbaDOS')
 *
 * @param {String} English country name as of the ISO standard
 * @return {String} Two-letter country code as of the ISO standard, uppercase
 * @api public
 */
exports.getCode = function(name) {
    return fromName[name.toUpperCase()];
};

/**
 * Get a country name for a country code. Case-insensitive.
 *
 * Examples:
 *
 *   // Returns 'TONGA'
 *   countrynames.getCode('TO')
 *   // Returns 'RÉUNION'
 *   countrynames.getCode('re')
 *
 * @param {String} Two-letter country code as of the ISO standard
 * @return {String} English country name as of the ISO standard, uppercase
 * @api public
 */
exports.getName = function(code) {
    return fromCode[code.toUpperCase()];
};

/**
 * Get all country information in an array of objects.
 *
 * Example:
 *
 *   // Returns an array [ { code: "AD", name: "ANDORA" }, ..., { code: "ZW", name: "ZIMBABWE" } ]
 *   countrynames.getAll();
 *
 * @return {Array} All two-letter country codes and names defined in the ISO standard
 * @api public
 */
exports.getAll = function() {
    return Object.keys(fromCode).slice(1).sort().map(function(code, index){
        return { 'code': code, 'name': fromCode[code] };
    });
}

/**
 * Get a country name for a country code. Case-insensitive.
 *
 * Example:
 *
 *   // Returns an array ["AD", ... "ZW"]
 *   countrynames.getAllCodes();
 *
 * @return {Array} All two-letter country codes defined in the ISO standard
 * @api public
 */
exports.getAllCodes = function() {
    return Object.keys(fromCode).slice(1).sort();
};

/**
 * Get a country name for a country code. Case-insensitive.
 *
 * Example:
 *
 *   // Returns an array ["AFGHANISTAN", ... "ZIMBABWE", "ÅLAND ISLANDS"]
 *   countrynames.getAllCodes();
 *
 * @return {Array} All country names in the ISO standard, sorted alphabetically in your locale, if available
 * @api public
 */
exports.getAllNames = function() {
    return Object.keys(fromName)
        .slice(1)
        .sort(function(a, b) {
            return a.localeCompare(b);
        });
};