how do i see if a big JSON object contains a value?

I'm using PHP to json encode a massive multi-dimensional array of events, so i get something like this:

var ents = {"7":{"event_id":"7","nn":"The Whisky Drifters","nn_url":"the-whisky-drifters",
  "venue":"The Grain Barge","date_num":"2010-06-11"开发者_JS百科,"date_txt":"Friday 11th June",
  "gig_club":"1","sd":"A New Acoustic String Band...","ven_id":"44",
  "art":0},"15":{"event_id":"15","nn":"Bass Kitchen","nn_url":"bass-kitchen",
  "venue":"Timbuk2","date_num":"2010-06-11","date_txt":"Friday 11th June",
  "gig_club":"2","sd":"Hexadecimal \/ DJ Derek \/ Id","ven_id":"21",
  "art":1},

the first dimension is the id, see

var ents = {"7":{

So it's possible to get the ids without examining the nested objects...

What's the fastest, most efficient way to check if my JSON contains an id?

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You can use the hasOwnProperty method:

if (ents.hasOwnProperty('7')) {
  //..
}

This method checks if the object contains the specified property regardless of its value.

Is faster than the in operator because it doesn't checks for inherited properties.

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Additionally to what CMS said: If you need all properties, you can loop over the porperties with for ... in:

for (prop in ents) {
  alert(prop); // Shows "7", "15", etc.
  // Accessing the sub-object:
  alert(ents[prop].nn); // Shows the names of each event
}

Also that isn't a "multi-dimensional array". It's an object (with more nested objects).

---

yes it is possible but you have to loop through complete json object on client side.

var JSONobj = ents, yourid;
for(key in JSONobj)
{
   if(((typeof key) == 'number') && key==yourid )
         alert(key);
}

if you are using jQuery then you can use $.each method to fetchng keys from jsonObject

   var JSONobj = ents, yourid;
        $.each(JSONobj, function(key, value){     
             if(((typeof key) == 'number') && key==yourid )
                 alert(key);
           //ids.push(key);
        });

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Just use myObject.has("keyName"). This is what really works.