Problem typecasting System.Object to boo.lang.hash in javascript

I am using javascript. One script with function "callfunction" returns me System.Object type that has a value {"status":"success","data":[{"id":"1","pass":"y"}]}. When I am assigning it to a var like this var vparse : boo.lang.hash = callfunction, I am getting an error that says problem typecasting sourcetype to destination type. I have tried converting the returned value to string and then assign to vparse. Again it says can't convert String to boo.lang.hash.