How do I convert object of javascript array in json format?

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jQuery

MVC4

I have a class AgeCriteria in that class i have 2 more classes like MinmumAge and MaximumAge.

how can i get below Json Format using Jquery.

"AgeCriteria": {
         "MinimumAge": {
            "Age": "50",
            "AgeUnitID": "2",
            "AgeUnit": "Year"
         },
         "MaximumAgemumAge": {
            "Age": "",
            "AgeUnitID": "",
            "AgeUnit": ""
         }
      }

What I have tried:

var _AgeCriteria=[];

 var MinAgeCriteria = { AgeType: "Min", Age: minAge, AgeUnitID: "1", AgeUnit: minUnit };
            _AgeCriteria.push(MinAgeCriteria);
            var MaxAgeCriteria = { AgeType: "Max", Age: maxAge, AgeUnitID: "1", AgeUnit: maxUnit };
            _AgeCriteria.push(MaxAgeCriteria);

above array give this result

[{"AgeType":"Min","Age":"15","AgeUnitID":"1","AgeUnit":"Year"},{"AgeType":"Max","Age":"25","AgeUnitID":"1","AgeUnit":"Year"}]