Sorting a JavaScript object by property name

I’ve been looking for a while and want a way to sort a Javascript object like this:

{
    method: 'artist.getInfo',
    artist: 'Green Day',
    format: 'json',
    api_key: 'fa3af76b9396d0091c9c41ebe3c63716'
}

and sort is alphabetically by name to get:

{
    api_key: 'fa3af76b9396d0091c9c41ebe3c63716',
    artist: 'Green Day',
    format: 'json',
    method: 'artist.getInfo'
}

I can’t find any code that will do this. Can anyone give me some help?

Answer

UPDATE from the comments:

This answer is outdated. In ES6 objects keys are now ordered. See this question for an up-to-date answer

By definition, the order of keys in an object is undefined, so you probably won’t be able to do that in a way that is future-proof. Instead, you should think about sorting these keys when the object is actually being displayed to the user. Whatever sort order it uses internally doesn’t really matter anyway.

By convention, most browsers will retain the order of keys in an object in the order that they were added. So, you could do this, but don’t expect it to always work:

function sortObject(o) {
    var sorted = {},
    key, a = [];

    for (key in o) {
        if (o.hasOwnProperty(key)) {
            a.push(key);
        }
    }

    a.sort();

    for (key = 0; key < a.length; key++) {
        sorted[a[key]] = o[a[key]];
    }
    return sorted;
}