use of hashtable in javascript

here is an example of usage of hashtable in javascript.For example I want to asociate specific buttonId
with specific grid Id I could create following hashtable:

 
var GridsButtons = { 
'AGroupsListGrid' :'DelA', 
'BGroupsListGrid' :'DelB' 
}; 

Then I could use it in code :

 var buttonid = GridsButtons[gid];