Jquery parseJSON - json

Hi - I am trying to parse a json object

I have 3 sets of data they are as follows

"from": {"name": "Bill Smith", "category": "Technology","id": "19292868552"}

"to": {"name": "Joe Hunt", "category": "Technology","id": "11204705797"}

"comments": {"name": "Sisi", "message": "Hi from Sisi", "id": "11204705797"},{"name": "Sara", "message": "Hi from Sarah", "id": "11204705797"}

I would like to create a json string/object and then have jquery parse the information

I can do it with 2 sets of data see code below...

Now i need to add the third set and parse/loop though though it!

Thanks in advance

------2 sets of data working!!!!-----------------------------------------------------
var obj = jQuery.parseJSON('{"from": {"name": "Bill Smith", "category": "Technology","id": "19292868552"}, "to": {"name": "Joe Hunt", "category": "Technology","id": "11204705797"}}');
alert(obj.from.name);
alert(obj.to.name);
-------------------------------------------------------------------------------------

'3 set of data I NEED HELP!!--------------------------------------------------------------

var obj = jQuery.parseJSON('{"from": {"name": "Bill Smith", "category": "Technology","id": "19292868552"}, "to": {"name": "Joe Hunt", "category": "Technology","id": "11204705797"}, "comments": [{"name": "Sisi", "message": "Hi from Sisi", "id": "11204705797"},{"name": "Sara", "message": "Hi from Sarah", "id": "11204705797"}]  }');

alert(obj.from.name);
alert(obj.to.name);

***THIS IS WHERE I GET LOST!! I need it to loop in comments and give an output (for each)
alert(obj.comments.message); - NOT WORKING

The output I hope for would be...
Message1 "Bill Smith"
Message2 "Joe Hunt"
Message3 "Hi from Sisi"
Message4 "Hi from Sarah"

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