javascript - Get name of key in keyvalue pair in JSON using jQuery? - Stack Overflow

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Say I have this JSON:

[
    {
        "ID": "1",
        "title": "Title 1",
    },
    {
        "ID": "2",
        "title": "Title 2",
    }
]

How would I return the set of key names that recur for each record? In this case, ID, title.

I tried:

$.getJSON('testing.json', function(data) {
  var items = [];
  $.each(data, function(key, val) {
    items.push(key +', ');
  });

  $('<p/>', {
     html: items.join('')
  }).appendTo('#content');
});

without success.

This is a JSON "database", and every "record" has the same keys. I just want a script that will tell me what the keys are, not test whether or not they occur in every entry.

Say I have this JSON:

[
    {
        "ID": "1",
        "title": "Title 1",
    },
    {
        "ID": "2",
        "title": "Title 2",
    }
]

How would I return the set of key names that recur for each record? In this case, ID, title.

I tried:

$.getJSON('testing.json', function(data) {
  var items = [];
  $.each(data, function(key, val) {
    items.push(key +', ');
  });

  $('<p/>', {
     html: items.join('')
  }).appendTo('#content');
});

without success.

This is a JSON "database", and every "record" has the same keys. I just want a script that will tell me what the keys are, not test whether or not they occur in every entry.

• javascript
• jquery
• json

Share Improve this question Follow edited Oct 21, 2017 at 11:10 Peter Mortensen 31.6k2222 gold badges110110 silver badges133133 bronze badges asked Apr 6, 2011 at 20:45 Dirk DigglerDirk Diggler 86511 gold badge1111 silver badges2323 bronze badges 1

• so youve got an array of json objects. you only want the shared keys right? so if the first had another pair 'key':'val' but the second did not, you do not want that returned. correcT? – jon_darkstar Commented Apr 6, 2011 at 20:54

Add a ment  | 

3 Answers 3

Sorted by: Reset to default 5

This will give you an array of all the string properties that match across an array of objects. Is that what you are looking for?

$.getJSON('testing.json', function(data) {
    var propertiesThatExistInAll = getPropertiesThatExistInAll(data);
});


var getPropertiesThatExistInAll = function(arr) {
    var properties = $.map(data[0], function (prop, value) {
        return prop;
    });

    var propertiesThatExistInAll = [];

    $.each(properties, function (index, property) {
        var keyExistsInAll = true;

        // skip the first one since we know it has all the properties
        for (var i = 1, len = data.length; i < len; i++) {
            if (!data[i].hasOwnProperty(property)) {
                keyExistsInAll = false;
                break;
            }
        }

        if (keyExistsInAll) {
            propertiesThatExistInAll.push(property);
        }
    });

    return propertiesThatExistInAll;
};

Something like this, perhaps?

items = [];
for (key in jsonobj) {
    if (!itemExists(items, key)) {
        items[items.length] = key
    }
}

function itemExists(items, value) {
    for (i = 0; i < items.length; i++) {
        if (items[i] == value) {
            return true
        }
    }
    return false;
}

Of course, that will return items that exist in any one of the objects, not that exist in all. It's not entirely clear from your question if this is the solution you want.

This can probably be made more efficient/concise, but the function below will do it.

var testJson = [ {'oi' : 1, 'arf': 2, 'foo' : 0}, {'oi': 5, 'arf': 7}];

function monKeys(j)
{

    var fillUp = [];
    for(var i in j[0])
       fillUp.push(i);

    for(var i = 1; i < j.length; i++)
    {
       var cur = j[i]; var curArr = [];
       for (var i in cur) {curArr.push(i)};
       fillUp = fillUp.filter(function(x) {return (curArr.indexOf(x) != -1);});
    }

    return fillUp;
}

alert(monKeys(testJson)); //oi,arf (not foo)

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