Iterating through a Dictionary to add to another

Question

I am trying to loop through each value in my dictionary and then go out and get another dictionary based on one of the objects in the first dictionary through each loop iteration:

var dAlbumPhotos = {};  // holds a list of photo objects
var dAlbumsAndPhotos = {}; // will hold all the album | dAlbumPhotos for each album

for(var a in dAlbums)
{
    dAlbumPhotos = GetPhotosForAlbum(userID, accessToken, a.id);

    dAlbumsAndPhotos(a) = dAlbumPhotos;
}

I'm not quite sure how to do this without an index. I need to increment through the dAlbumPhotos and append to the final dictionary that album and it's dAlbumPhotos

Answer 1

A for..in loop gives you back the indexes, not the objects in the loop. That is, a.id is likely nonsensical -- you really mean dAlbums[a].id. It follows that dAlbumsAndPhotos[a] is probably where you need to store the results.

Answer 2

I think this is what you're after:

var dAlbumPhotos = {};  // holds a list of photo objects
var dAlbumsAndPhotos = {}; // will hold all the album | dAlbumPhotos for each album

for(var a in dAlbums)
{
    dAlbumPhotos = GetPhotosForAlbum(userID, accessToken, dAlbums[a]);

    dAlbumsAndPhotos[a] = dAlbumPhotos;
}

Answer 3

It looks like you're really using an Associative Array in Javascript so you should be able to change the last bit of your code to be:

for(var a in dAlbums)
{
    dAlbumPhotos = GetPhotosForAlbum(userID, accessToken, dAlbums[a].id);
    dAlbumsAndPhotos[a] = dAlbumPhotos;
}

Answer 4

Suppose you have the photo data in a json table like this:

var dPhotos = [{src: "/photos/a.jpg", album: "animals"}, {src: "/photos/b.jpg", album: "landscapes"}];

Then you can use jOrder to extract the group index like this:

var table = jOrder(dPhotos)
    .index('album', ['album'], {grouped: true});

var index = table.index('album').flat();

This index will hold a dictionary with album names associated with the a list of ids of rows in dPhotos belonging to that album.

jOrder is available from http://github.com/danstocker/jorder