How to check if an answer (date) is a json

Question

How can I check if a result (date) coming from an ajax request is a json or not? I tried this code but did not succeed

var obj = $.parseJSON(response);

            if(obj.avatar) {
            } else {
            }

Answer 1

The method parseJSON jQuery raises an exception if JSON is not valid. Therefore:

var obj;
try {
    obj = $.parseJSON(response);
    // use o JSON aqui
} catch(ex) {
    // trate o erro aqui
}

Answer 2

A solution with native Javascript suggested in the Soen would be:

function testarJSON (jsonString){
    try {
        var o = JSON.parse(jsonString);
        if (o && typeof o === "object" && o !== null) return o;
    }
    catch (e) { }
    return false;
};

Example:

var jsonValido = '{ "time": "03:53:25 AM", "milliseconds_since_epoch": 1362196405309, "date": "03-02-2013" }';
var jsonInvalido = '"time": "03:53:25 AM", "milliseconds_since_epoch": 1362196405309, "date": "03-02-2013"';

function testarJSON (jsonString){
    try {
        var o = JSON.parse(jsonString);
        if (o && typeof o === "object" && o !== null) return o;
    }
    catch (e) { }
    return false;
};

alert('Nr de JSONs válidos: ' + [jsonValido, jsonInvalido].filter(testarJSON).length);