Hashmap module in node.js?

Ok, I have tried searching the web for different modules for me to use but it didn't make me any wiser. There where so many different alternatives and I couldn't find any good discussion on wich was the better.

I need a hashmap with a 5 digit decimal number as key, and with arrays as values. I need to effectively iterate through its keys as well a couple of times per second.

Anyone have a good recommendation of what I should use?

Thank you! //Svennisen

I realised I do not need a module at all. Since in javascript an array with a string index is automatically considered a map with key,value instead of index,value.

So I just convert my number to a string and use an ordinary vector.