Basic usage of AES with Output Feedback

aes-ofb.js

/// Use public CDN in your frontend <script type="text/javascript" src="https://cdn.rawgit.com/ricmoo/aes-js/e27b99df/index.js"></script>

// Convert it to base 36 (numbers + letters), and grab the first 9 characters
// after the decimal.
var randomStringGenerator = function (length, prefix) {
	return (prefix == undefined ? 'key-' : prefix) + Math.random().toString(36).substr(2, (length == undefined ? 5 : length));
}

// Get ASCII numbers from a string as array
var stringToAscii = function(input){
	var result = [];
	for (var key in input) {
		if (input.hasOwnProperty(key)) {
			result.push(input[key].charCodeAt());
		}
	}
	return result;
}

var keyGenerator = function(){
	return stringToAscii(randomStringGenerator(12)).join(':');
}

var ivGenerator = function(){
	return stringToAscii(randomStringGenerator(10, 'keyiv-')).join(':');
}

var encrypt = function (cipherText){
	var textBytes = aesjs.utils.utf8.toBytes(cipherText);
	var aesOfb = new aesjs.ModeOfOperation.ofb(key, iv);
	var encryptedBytes = aesOfb.encrypt(textBytes);
	return aesjs.utils.hex.fromBytes(encryptedBytes);
}

var decrypt = function(mesage){
	var encryptedBytes = aesjs.utils.hex.toBytes(message);
	var aesOfb = new aesjs.ModeOfOperation.ofb(key, iv);
	var decryptedBytes = aesOfb.decrypt(encryptedBytes);
	return aesjs.utils.utf8.fromBytes(decryptedBytes);
}

var key = '';
var iv = '';

$(document).ready(function () {
	
	key = keyGenerator();
	iv = ivGenerator();
	
	console.log(`Your Key: ${key}`);
	console.log(`Your IV: ${iv}`);
	
	do {
		key = prompt('Insert your key:');
	} while (key == null);
	do {
		iv = prompt('Insert your IV:');
	} while (iv == null);
	
	// Get an array from given strings
	key = key.split(':').map(function (value) { return parseInt(value) });
	iv = iv.split(':').map(function (value) { return parseInt(value) });
});

why did you miss the 's' in line 35? That decrypt function would not work.

35: var decrypt = function(mes age){