How to create a multimap/hashtable in JQuery?

How to create a multimap/hashtable in JQuery?

Hi,
I need a data structure in JQuery/Javascript that has a {key, values} pairing. I need it to be able to  have multiple objects with the same key. For example, a business type key holding all google map markers created for that business type. 

I would also know how to use such a data structure's get and set.

Thanks in advance.