Parsing and retrieving the values from JSON object in node.js

Possible Duplicate:
Accessing nested JavaScript objects with string key

I am trying to parse a JSON object and retrieve the values from it. The JSON structure is as follows

"projects": {

 "P116805": {

    "id": "P116805",

    "regionname": "AFRICA",

    "lendinginstr": "Specific Investment Loan",

    "project_name": "Capacity Building for Regional Coordination of Sustainable Forest Management in the Congo Basin under the GEF Program for the Congo",

    "closingdate": "2013-06-30T00:00:00Z",

    "lendprojectcost": "1,920,000",

    "totalamt": "0",

    "grantamt": "820,000",

    "url": "http://www.worldbank.org/projects/P116805/capacity-building-regional-coordination-sustainable-forest-management-congo-basin-under-gef-program-congo?lang=en",

    "countrycode": "3A",

    "countryname": "Africa"

}

I am trying to get the value of 'regionname' within Projects/P116805. I get the key name to be parsed on runtime as projects.P116805.regionname. I store that in a variable and use that for parsing.

I am trying to parse the value as follows

var obj = JSON.parse(response);
var key = projects.P116805.regionname;

I can get these values as projects.P116805.regionname but in my case i am not able to do that.If i use obj.key, i am not getting the correct values. Can anyone help me resolve this issue.