Using a variable as identifier in a json array

I'm wondering if it is possible to use assigned variables as identifier in a json array. When I tried this, I was getting some unexpected results:

(Code is 开发者_高级运维simplified, parameters are passed in a different way)

var parameter = 'animal';
var value = 'pony';

Util.urlAppendParameters(url, {
  parameter: value
});


Util.urlAppendParameters = function(url, parameters) {
  for (var x in parameters) {
    alert(x);
  }
}

Now the alert popup says: 'parameter' instead of 'animal'. I know I could use a different method (creating an array and assigning every parameter on a new line), but I want to keep my code compact.

So my question is: Is it possible to use a variable as an identifier in the json array, and if so, could you please tell me how?

Thanks in advance!

You will need to build your object in two steps, and use the [] property accessor:

var parameter = 'animal';
var value = 'pony';

var obj = {};
obj[parameter] = value;

Util.urlAppendParameters (url, obj);

I don't think JSON Array is the more correct term, I would call it Object literal.

No, you can't use a variable as an identifier within an object literal like that. The parser is expecting a name there so you can't do much else but provide a string. Similarly you couldn't do something like this:

var parameter = 'animal';
var parameter = 'value'; //<- Parser expects a name, nothing more, so original parameter will not be used as name

The only work around if you really really want to use an object literal on a single line is to use eval:

Util.urlAppendParameters (url, eval("({" + parameter + " : value})");

Depending on your needs you could also build your object with a helper function;

Util.createParameters = function(args) {
    var O = {};
    for (var i = 0; i < arguments.length; i += 2)
        O[arguments[i]] = arguments[i + 1];
    return O
}

Util.urlAppendParameters (url, Util.createParameters(parameter, value, "p2", "v2"));