This isn't a single JSON object. You have an array of JSON objects. You need to loop over array first and then access each object. Maybe the following kickoff example is helpful:

var arrayOfObjects = [{
  "id": 28,
  "Title": "Sweden"
}, {
  "id": 56,
  "Title": "USA"
}, {
  "id": 89,
  "Title": "England"
}];

for (var i = 0; i < arrayOfObjects.length; i++) {
  var object = arrayOfObjects[i];
  for (var property in object) {
    alert('item ' + i + ': ' + property + '=' + object[property]);
  }
  // If property names are known beforehand, you can also just do e.g.
  // alert(object.id + ',' + object.Title);
}

If the array of JSON objects is actually passed in as a plain vanilla string, then you would indeed need eval() here.

var string = '[{"id":28,"Title":"Sweden"}, {"id":56,"Title":"USA"}, {"id":89,"Title":"England"}]';
var arrayOfObjects = eval(string);
// ...

To learn more about JSON, check MDN web docs: Working with JSON .

// You can declare restaurants as an array of restaurant objects
restaurants = 
[
    {
        "location" : "123 Road Dr", 
        "city_state" : "MyCity ST", 
        "phone" : "555-555-5555", 
        "distance" : "1" 
    },
    {
        "location" : "456 Avenue Crt", 
        "city_state" : "MyTown AL", 
        "phone" : "555-867-5309", 
        "distance" : "0" 
    }
];

// Then operate on them with a for loop as such
for (var i = 0; i< restaurants.length; i++) {
    restaurants[i].distance = restaurants[i].distance; // Or some other logic.
}

// Finally you can sort them using an anonymous function like this
restaurants.sort(function(a,b) { return a.distance - b.distance; });

var json_data = {"2013-01-21":1,"2013-01-22":7};
var result = [];

for(var i in json_data)
    result.push([i, json_data [i]]);


var data = new google.visualization.DataTable();
data.addColumn('string', 'Topping');
data.addColumn('number', 'Slices');
data.addRows(result);

http://jsfiddle.net/MV5rj/