How to synchronize a client-only collection with a shared collection in Meteor. Doesn't handle callbacks other than added, but should do what it's supposed to do.

Meteor local mirror

//common to client and server
SharedCollection = new Meteor.Collection('shared');

//client from here on out

LocalMirror = new Meteor.Collection(null);

var createLocalFromShared = function(doc) {
    // create a new id for the local doc, but store the old one
    doc.sharedId = doc._id;
    delete doc._id;
    LocalCollection.insert(doc);
};

// should only run this once, and before a subscription has pulled 
// the shared data from the server.  Otherwise I'm not sure that 
// the added callback will do the initial populate step.
SharedCollection.find().observe({
    added: function(doc,beforeIndex) {
        if (LocalCollection.findOne({sharedId: doc._id})) {
            console.log('already have a local doc with that id...');
            return;
        }
        createLocalFromShared(doc);
    },
});