How to handle JSON object

[ESA14]

I have a few in-app purchases in my app.
How can I check which of this purchases a user owns?
I think I must get the productid from the JSON object, but how?
I tried:
inappbilling.getPurchases(successHandler, fail);

function successHandler (result) {
strResult = JSON.parse(result);
alert(strResult.productId);
}

This doesn't work.

Please help me.

[srthakkar]

Hey ESA14,

Use JSON.stringify(result) instead of JSON.parse(result).