How to check key exist in json or not [duplicate]

Question

I have JSON object and i want to check key is set in that JSON object

Here is JSON object

var Data_Array = {
    "Private": {
        "Price": {
            "Adult": "18",
            "Child": [{
                "FromAge": "0",
                "ToAge": "12",
                "Price": "10"
            }]
        }
    }
}

If JSON Object like this as you can see Child is not exist, then how to check this

var Data_Array = {
    "Private": {
        "Price": {
            "Adult": "18"
        }
    }
}

I have tried

if(Data_Array.Private.Price.Child[0].Price != "undefined"){
    ...
}

But it is showing me this error

Uncaught TypeError: Cannot read property

I am not be able to find out what should i do.