Why is JSON.parse not outputing the correct result? - json

Question

Here's my code:
var jsonStr = (JSON.stringify(data, ['flightPositions', 'flightId', 'positions', 'lat', 'lon', 'date'], 4));
alert(jsonStr);
var jsonObj = JSON.parse(jsonStr);
alert(jsonObj.flightPositions);
},
The output from JSON.stringify seems to be correct. I've run it through JSLint and gives me no error:
{
"flightPositions": [
{
"flightId": 621650693,
"positions": [
{
"lat": 40.4272,
"lon": -74.3395,
"date": "2015-10-31T13:31:55.000Z"
},
{
"lat": 40.6833,
"lon": -74.1667,
"date": "2015-10-31T13:32:00.000Z"
},
{
"lat": 40.6133,
"lon": -74.0122,
"date": "2015-10-31T13:32:55.000Z"
},
{
"lat": 40.7538,
"lon": -74.0989,
"date": "2015-10-31T13:33:55.000Z"
},
{
"lat": 40.8125,
"lon": -74.1044,
"date": "2015-10-31T13:34:55.000Z"
},
{
"lat": 40.8147,
"lon": -74.1832,
"date": "2015-10-31T13:35:55.000Z"
},
{
"lat": 40.7624,
"lon": -74.2316,
"date": "2015-10-31T13:36:55.000Z"
},
{
"lat": 40.6829,
"lon": -74.2523,
"date": "2015-10-31T13:37:55.000Z"
}
]
},
{
"flightId": 621650363,
"positions": [
{
"lat": 40.7859,
"lon": -74.0978,
"date": "2015-10-31T13:29:21.000Z"
},
{
"lat": 40.7738,
"lon": -74.143,
"date": "2015-10-31T13:30:21.000Z"
},
{
"lat": 40.7169,
"lon": -74.1948,
"date": "2015-10-31T13:31:21.000Z"
},
{
"lat": 40.6602,
"lon": -74.2524,
"date": "2015-10-31T13:32:21.000Z"
},
{
"lat": 40.5888,
"lon": -74.3109,
"date": "2015-10-31T13:33:21.000Z"
},
{
"lat": 40.5004,
"lon": -74.3464,
"date": "2015-10-31T13:34:21.000Z"
},
{
"lat": 40.4213,
"lon": -74.3074,
"date": "2015-10-31T13:35:21.000Z"
},
{
"lat": 40.3152,
"lon": -74.2497,
"date": "2015-10-31T13:36:21.000Z"
},
{
"lat": 40.2224,
"lon": -74.1577,
"date": "2015-10-31T13:37:21.000Z"
},
{
"lat": 40.163,
"lon": -74.0203,
"date": "2015-10-31T13:38:21.000Z"
}
]
},
{
"flightId": 621650734,
"positions": [
{
"lat": 40.6742,
"lon": -74.1728,
"date": "2015-10-31T13:29:15.000Z"
},
{
"lat": 40.6369,
"lon": -74.1976,
"date": "2015-10-31T13:30:15.000Z"
},
{
"lat": 40.7258,
"lon": -74.1342,
"date": "2015-10-31T13:30:22.000Z"
},
{
"lat": 40.8227,
"lon": -74.0561,
"date": "2015-10-31T13:32:15.000Z"
},
{
"lat": 40.7436,
"lon": -74.2853,
"date": "2015-10-31T13:33:15.000Z"
},
{
"lat": 40.6199,
"lon": -74.2754,
"date": "2015-10-31T13:34:15.000Z"
},
{
"lat": 40.5328,
"lon": -74.2924,
"date": "2015-10-31T13:35:15.000Z"
},
{
"lat": 40.4304,
"lon": -74.2721,
"date": "2015-10-31T13:36:15.000Z"
},
{
"lat": 40.3341,
"lon": -74.2384,
"date": "2015-10-31T13:37:15.000Z"
},
{
"lat": 40.2547,
"lon": -74.173,
"date": "2015-10-31T13:38:15.000Z"
}
]
},
{
"flightId": 621633505,
"positions": [
{
"lat": 40.3481,
"lon": -74.7084,
"date": "2015-10-31T13:29:35.000Z"
},
{
"lat": 40.3788,
"lon": -74.6202,
"date": "2015-10-31T13:30:35.000Z"
},
{
"lat": 40.4126,
"lon": -74.5206,
"date": "2015-10-31T13:31:35.000Z"
},
{
"lat": 40.4436,
"lon": -74.4448,
"date": "2015-10-31T13:32:35.000Z"
},
{
"lat": 40.45,
"lon": -74.4333,
"date": "2015-10-31T13:32:35.000Z"
},
{
"lat": 40.481,
"lon": -74.3348,
"date": "2015-10-31T13:33:47.000Z"
},
{
"lat": 40.5225,
"lon": -74.2702,
"date": "2015-10-31T13:34:47.000Z"
},
{
"lat": 40.5691,
"lon": -74.2228,
"date": "2015-10-31T13:35:47.000Z"
},
{
"lat": 40.6234,
"lon": -74.1737,
"date": "2015-10-31T13:36:47.000Z"
},
{
"lat": 40.6804,
"lon": -74.1765,
"date": "2015-10-31T13:37:47.000Z"
}
]
},
{
"flightId": 621650749,
"positions": [
{
"lat": 40.6906,
"lon": -74.2433,
"date": "2015-10-31T13:34:54.000Z"
},
{
"lat": 40.631,
"lon": -74.5142,
"date": "2015-10-31T13:35:54.000Z"
},
{
"lat": 39.6624,
"lon": -74.6148,
"date": "2015-10-31T13:36:54.000Z"
},
{
"lat": 40.6833,
"lon": -74.1667,
"date": "2015-10-31T13:37:00.000Z"
},
{
"lat": 40.7207,
"lon": -74.1416,
"date": "2015-10-31T13:37:54.000Z"
}
]
}
]
}
alert output from JSON.stringify
However, I am getting the following for the JSON.parse:
[object Object],[object Object],[object Object],[object Object],[object Object]
What could be wrong here?
UPDATE
Changed alert to console.log (without concatenating string) and it gives me the following output:
Array [ Object, Object, Object, Object, Object ]
console

Answer 1

Your code to stringify and parse JSON is correct, the behavior you are seeing is due to the alert function. alert automatically tries to convert the parameter to a human-readable string (not a JSON string), in your case it converts every item inside the flightPositions array to string.
To debug JS you should use the console.log method (docs) and the browser developer's tools (use F12 to open the tools).
var jsonStr = (JSON.stringify(data, ['flightPositions', 'flightId', 'positions', 'lat', 'lon', 'date'], 4));
console.log(jsonStr);
var jsonObj = JSON.parse(jsonStr);
console.log(jsonObj.flightPositions);