var str = 'Hello world';
var letters = {'a':'4', 'e':'3','o':'0'};
for (var letter in letters) {
var regex = new RegExp(letter, 'g');
str = str.replace(regex, letters[letter]);
}
print(str);
dmFyIHN0ciA9ICdIZWxsbyB3b3JsZCc7CnZhciBsZXR0ZXJzID0geydhJzonNCcsICdlJzonMycsJ28nOicwJ307CmZvciAodmFyIGxldHRlciBpbiBsZXR0ZXJzKSB7Cgl2YXIgcmVnZXggPSBuZXcgUmVnRXhwKGxldHRlciwgJ2cnKTsKCXN0ciA9IHN0ci5yZXBsYWNlKHJlZ2V4LCBsZXR0ZXJzW2xldHRlcl0pOwp9CnByaW50KHN0cik7