Passing a external variable in JSON.parse function

Question

I am trying to get a value from json by using the JSON.parse function. My json response is given below:

{
  "rows": 10,
  "os": "0",
  "page": "1",
  "total": "122",
  "projects": {
    "P143841": {
      "id": "P143841",
      "locations": [{
        "geoLocId": "0002220957",
        "latitude": "3.866667",
        "longitude": "11.516667"
      }],
    }
  }
}

I am able to get the value 10 if I do JSON.parse(obj.rows) but if I assign the rows to a variable say var value = rows and then I pass it to the JSON.parse(obj.value) function I got undefined.

P.S. I won't be knowing the names of the response parameters, i.e. i won't know if it will be rows or os quoting from the above example. I will be retrieving them from a database. If I perform the code below:

  for (var i=0;i<length;i++) {
    var value = responseParam_array[i];
    console.log(obj.value);
  }

I get the output but any help will be much appreciated.

score 6 · Accepted Answer · answered Jan 22 '13 at 11:12

6

As per the other answers you shouldn't need to parse individual properties, just parse the original JSON and then operate on the resulting object.

But as for this problem:

"if I assign the rows to a variable say var value = rows and then I pass it to the JSON.parse(obj.value) function I got undefined"

If value is a variable holding the name of a property of obj then you need:

obj[value]
// NOT
obj.value

When you use "dot" notation the part on the right of the dot is taken as the literal name of the property, not as a variable. Using the square-bracket syntax the expression in the brackets is evaluated and its result is taken as the property name.

answered Jan 22 '13 at 11:12

nnnnnn

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I did as u suggested.But if i have to parse say obj.projects.P143841.locations[0].latitude and if i pass it into obj[value] i get as undefined. (ie) obj[projects]will be printed but obj[projects.P143841.locations[0].latitude] is throwing undefined.Any suggestion will be really helpful – Amanda G Jan 22 '13 at 11:48
1

Try `obj[projects].P143841.locations[0].latitude`. If you're chaining multiple properties like that each one needs to use either dot notation or brackets, don't put the whole chain of names inside the same set of brackets. `obj[projects]["P143841"]["locations"][0].latitude` (and other variations) will also work. – nnnnnn Jan 22 '13 at 21:59

score 1 · Answer 2 · answered Jan 22 '13 at 10:44

you should be json-parsing your whole object and using the parsed object afterwards (you dont need to parse every property for itself)

var strObj = '{"rows": 10,"os": "0","page": "1","total": "122","projects":{"P143841":{"id":"P143841",}}';

var obj = JSON.parse(strObj);
var rows = obj.rows;

hunterloftis · Answer 3 · 2013-01-22T10:49:18.353

0

If I understand your question:

var str = '{ "some": "JSON String like the one above with", "rows": 10 }';
var parsed = JSON.parse(str);
var whatYouWant = parsed.rows;

edited Jan 22 '13 at 10:49

answered Jan 22 '13 at 10:43

hunterloftis

13,386
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Passing a external variable in JSON.parse function

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