CODEWITHSUNDEEP
javascriptjson
Justin Davis
Justin Davis

Reputation: 305

How do I retrieve a key from a JSON response, when I don't know the key value?

This may be really simple, but I've beat my head against the wall trying to figure it out.

I need to grab a value from a JSON response, but the key returned in the response is random, so I can't directly reference it to drill into it.

Here's the response I'm getting back:

var c = {
         "success": { 
                    "7d40ab5352b0471cae5bdefc2e032840": { 
                          "__type__" : "user",
                          "__id__" : "7d40ab5352b0471cae5bdefc2e032840"
                    }

         },
         "errors": {}
         }

What I need is the random string you see there - the ID. I've tried all kinds of things, and cannot for the life of me figure out how to get the ID back as a string. I've tried getting at it with array notation c.success[0][0] to no avail. Obviously, I can't use dot notation, since I don't know what to put after .success.

Anyone know what to do in a situation where the keys of the array aren't known beforehand? I want to make sure that I do this in a way that's considered the best practice, not a hack.

Thanks...and if I've somehow missed an answer to this that's otherwise published, please send me that way. I've searched for days and can't find this answer.

Upvotes: 2

Views: 147

Answers (3)

Brett Zamir
Brett Zamir

Reputation: 14345

for (var prop in c.success) {
  alert(c.success[prop].__id__); // Replace the alert with whatever you want to do with the ID
  // break; // Uncomment if there can be more than one ID returned and you only want one
}

and if the key is the same as the __id__ value, you can simply do:

for (var prop in c.success) {
  alert(prop); // Replace the alert with whatever you want to do with the ID
  // break; // Uncomment if there can be more than one ID returned and you only want one
}

Although Šime Vidas's use of Object.keys is more elegant, you will need the above code to work in older browsers unless you use what is called a him (i.e., you add some extra code which lets you use new standards today--i.e., an implementation of Object.keys which does the same thing as I did above, unless a built-in version already exists, in which case the shim will give preference to the built-in version).

Upvotes: 2

Bergi
Bergi

Reputation: 664548

You can use a simple loop:

for (var id in c.success) {
    var obj = c.success[id];
    // do something
}

If you want to ensure that only the first property in the object will be handled, you can add a break; statement in the end.

Upvotes: 0

Šime Vidas
Šime Vidas

Reputation: 185923

This:

var obj = c.success[ Object.keys( c.success )[0] ];

obj.__type__ // "user"
obj.__id__ // "7d40ab5352b0471cae5bdefc2e032840"

Live demo: http://jsfiddle.net/AJaBS/

Upvotes: 2

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