Getting the value of an object's property where the key is a blank string

Question

Given this object:

: http://www.w3.org/2005/Atom
gd: http://schemas.google.com/g/2005 
openSearch: http://a9.com/-/spec/opensearch/1.1/ 
app: http://www.w3.org/2007/app; 
media: http://search.yahoo.com/mrss/

How do I get the value of the first property? I suspect this is an easy process, but I'm drawing a blank. Thanks in advance.

The object is built as such:

Server side (php):

$namespaces = $feedXML->getNamespaces(true);
$arr = array(
'Status' => 'Success',
'Message' => 'Feed fetched.',
'Namespaces' => $namespaces,
'Feed XML' => $feedXML
);
echo json_encode($arr);

Client side (JS):

   var output = '';
    for (property in dataj["Namespaces"]) {
        output += property + ': ' + dataj["Namespaces"][property] + '; ';
    }
    alert(output);

I would like to be able to check the namespaces to see if this is Atom or RDF.

It sounds like just iterating each property is going to be the best way.

Does that code actually work? Because all I get is [Uncaught SyntaxError: Unexpected token `:`](http://jsfiddle.net/davidThomas/4kNhP/). — David Thomas, Dec 12 '12 at 21:20
This is not valid JavaScript object. And I am sure the api sends the properly encoded JSON object (e.g. `{"xmlns": "http://www.w3.org/2005/Atom", "xmlns$gd": "http://schemas.google.com/g/2005"}`). — Salman A, Dec 12 '12 at 21:21
Can you post (relevant part of) the JSON generated by your PHP script? — Salman A, Dec 12 '12 at 21:29

score 10 · Accepted Answer · answered Dec 12 '12 at 21:17

10

If you're trying to get the value of the property whose key is an empty string, then you can do

var value = myObject[''];

If you try to get the "first property" of an object, you can't because properties in javascript objects aren't ordered.

answered Dec 12 '12 at 21:17

Denys Séguret

372,613
87
782
758

This is a JSON object of the namespaces XML namespaces. Are you saying I should decode this object back to an array? Would that even work with a blank key? – Drazisil Dec 12 '12 at 21:20
This is correct, however you could iterate over the object's properties to get at the value. – Mike Brant Dec 12 '12 at 21:20
Did not know you could reference an empty string key that way. Thanks. – Drazisil Dec 12 '12 at 21:41

score 1 · Answer 2 · edited May 23 '17 at 12:32

1

Properties aren't guaranteed to be ordered. You can however iterate over all properties to find the right one (if you know what you are looking for):

for(var prop in obj) {
    if(obj.hasOwnProperty(prop))
        doSomethingWith(obj[prop]);
}

Reference: Iterating over every property of an object in javascript using Prototype?

Then get the key by

var value = obj[key];

edited May 23 '17 at 12:32

Community

1
1

answered Dec 12 '12 at 21:20

Peter Rasmussen

16,474
7
46
63

https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Object/hasOwnProperty This doesn't look like it would would on what appears to be a blank property. – Drazisil Dec 12 '12 at 21:38

score 1 · Answer 3 · answered Dec 12 '12 at 21:25

1

You can try this code:

var test_bject = {'test': 1, 'test2': 2, 'test3': 3}, first_value;

for (i in test) {
  first_value = test_object[i];
  break;
}

answered Dec 12 '12 at 21:25

Dmitri Pavlutin

18,122
8
37
41

That would work. I should have better worded what I was trying to do. – Drazisil Dec 12 '12 at 21:46

Getting the value of an object's property where the key is a blank string

3 Answers3

Linked