collection

A collection field produces a component that in turn renders a list of child components. It executes a query to get all of the child facts, and uses them as the starting point of the child mapping.

{
    Messages: collection(j.for(messagesInChannel), messageMapping)
}

Give collections a capitalized name so that you can use them as regular React components within your render function.

const channelMapping = channelSpec(({ Messages }) => (
    <Messages />
));

You can order the collection by a field of the resulting fact using the ascending or descending functions.

{
    Messages: collection(j.for(messagesInChannel), messageMapping,
        descending(m => m.sentAt))
}

Or you can order by the results of another query. The order-by query starts from the result.

{
    Messages: collection(j.for(messagesInChannel), messageMapping,
        ascending(j.for(messageSender).then(namesOfUser), n => n.value))
}