Very simple user authentication using async

auth.js

var async = require('async');

module.exports = {
	userCredentials: [
	{
		username: 'testUser1',
		password: 'pa$$word'
	},	
	{
		username: 'testUser2',
		password: 's0mep4$$w0rd'
	}],	

	isUserAuthenticated: function(username, password) { 
		var scope = this;
		process.nextTick(function() {
			async.detect(
				scope.userCredentials,
				
				function(item, callback) {
					var isCorrect = item.username === username &&
						item.password === password;
					callback(isCorrect);
				},
				
				function(result) {
					if(!result) {
						throw "Username and password incorrect";
					}
					
					console.log("Username and password are correct");
				}
			);
		})
	}
}

main.js

var async = require('async'),
	auth = require('./auth.js'),
	stdin = process.stdin, stdout = process.stdout;
	
process.stdin.resume();
process.stdin.setEncoding('utf8');
		
async.waterfall([
	function(callback) {
		stdout.write("Please enter your username: ");
		stdin.once('data', function(data) {
			username = data.toString().trim();
			
			if(username === '') {
				callback("Username cannot be blank");
			}
			
			callback(null, username);
		})
	},
	function(username, callback) {
		stdout.write("Please enter your password: ");
		stdin.once('data', function(data) {
			var password = data.toString().trim();
			
			if(password === '') {
				callback("Password cannot be blank");
			}
			
			callback(null, {
				username: username,
				password: password
			});
		})
	}
], function(err, credentials) {
	if(err) {
		throw err;
	}
	auth.isUserAuthenticated.call(auth, credentials.username, credentials.password);
})