gistfile1.txt

var newUploads = Immutable.fromJS(action.value);
// assuming oldUploads is the previous value.

var changeWithStates = newUploads.map(newValue => {
    var oldValue = oldUploads.find(other => other.id === newValue.get('id'));

    if (oldValue.get('complete') === false && newValue.has('error')) {
        return newValue.set('status', 'errored');
    }
});