mercury/examples/unidirectional/backbone/observ-backbone.js

A truly modular frontend framework

'use strict';

/* This is a reference implementation of how to recursively
    observ a Backbone.Model.

    A proper implementation is going to need a bunch of
    performance optimizations

*/
module.exports = toObserv;

// given some model returns an observable of the model state
function toObserv(model) {
    // return an obect
    return function observ(listener) {
        // observ() with no args must return state
        if (!listener) {
            return serialize(model);
        }

        // observ(listener) should notify the listener on
        // every change
        listen(model, function serializeModel() {
            listener(serialize(model));
        });
    };
}

// convert a Backbone model to JSON
function serialize(model) {
    var data = model.toJSON();
    Object.keys(data).forEach(function serializeRecur(key) {
        var value = data[key];
        // if any value can be serialized toJSON() then do it
        if (value && value.toJSON) {
            data[key] = data[key].toJSON();
        }
    });
    return data;
}

// listen to a Backbone model
function listen(model, listener) {
    model.on('change', listener);

    model.values().forEach(function listenRecur(value) {
        var isCollection = value && value._byId;

        if (!isCollection) {
            return;
        }

        // for each collection listen to it
        // console.log('listenCollection')
        listenCollection(value, listener);
    });
}

// listen to a Backbone collection
function listenCollection(collection, listener) {
    collection.forEach(function listenModel(model) {
        listen(model, listener);
    });

    collection.on('add', function onAdd(model) {
        listen(model, listener);
        listener();
    });
}