Ordering in javascript

Question

How easy/hard is it to order collections in javascript (alphabetical and numerically).

Say I have a collection like:

var map = {

    user: { id: "23434", username: "mrblah" },
    user: { id: "1010", username: "johnskeet" }

};

And I want to order the collection by id and username.

Update correction thanks:

var map = [ { id: "23434", username: "mrblah" }, { id: "1010", username: "johnskeet" } ];

Answer 1

var map = { 
    users: [
        { id: "23434", username: "mrblah" },
        { id: "1010", username: "johnskeet" }
    ]
};

map.users.sort(function(a, b) { 
    return a.id - b.id; 
});

map.users.sort(function(a, b) { 
    return a.username.localeCompare(b.username); 
});

Answer 2

You want your object to be an array:

var map = [
    { id: "23434", username: "mrblah" },
    { id: "1010", username: "johnskeet" },
    { id: "1220", username: "alohaguy" }
];

We need a utility to display the usernames in order so we can test our work:

var displayUsernames = function(map) {
    var out = [];
    for (var i=0;i<map.length;i++) {
     out.push((map[i].username));
    }
    alert(out.join(', '));
};

If we use it: displayUsernames(map); we get mrblah, johnskeet, alohaguy

Since it's an array, so we can use .sort(), like this: map.sort();, but if we do that we still get:

mrblah, johnskeet, alohaguy

...from displayUsernames(map); because the array of objects can't be sorted the same way as if it were an array of numbers or strings.

However, if we pass the sort() function a comparison function...

var myCompareFunction = function(a, b) {
    return a.username.localeCompare(b.username);
};

Then pass it into map.sort()

map.sort(myCompareFunction);

Now, when we display it again with displayUsernames(map); we get alohaguy, johnskeet, mrblah

Hope that helps.