Backbone.Memoize

Lazy-ass caches for Backbone collections and models. It works like Underscore's memoize but invalidates with the appropriate Backbone events. This is especially useful for complex computations.

Installation

$ bower install backbone-memoize --save

or include index.js with script tag.

Example

var Employees = Backbone.Collection.extend({
  initialize: function() {},

  best: function() {
    return this.max(function(user) {
      return this.factorial(user.get('rating'));
    });
  },

  // standard factorial implementation, as example of pure function
  // http://en.wikipedia.org/wiki/Factorial
  factorial: function(n) {
    return n <= 1 ? 1 : n * this.factorial(n - 1);
  }
});

Backbone.Memoize(Employees, ['best', 'factorial'], {
  best: 'add remove change:rating', // setup specific events for method
  factorial: false // pure function and we never reset the cache
});

var employees = new Employees([
  { id: 1, rating: 8, type: 'CEO',       name: 'Adam' },
  { id: 2, rating: 4, type: 'CTO',       name: 'Liza' },
  { id: 3, rating: 7, type: 'sales',     name: 'Anna' },
  { id: 4, rating: 0, type: 'sales',     name: 'Tobi' },
  { id: 5, rating: 1, type: 'developer', name: 'Rian' },
  { id: 6, rating: 6, type: 'QA',        name: 'Jess' }
]);

// Functions work with all methods as usual, except now the results are stored
// in memory, and the app works much faster in cases where function execution
// is particularly expensive.
employees.best(); // User(1)

// Same result, but without expensive filtering
employees.best(); // User(1)

// When collection members are added, removed, or updated, the cache is reset
employees.get(5).set('rating', 10);
employees.best(); // User(5)

Backbone.Memoize(Klass, methods, [options])

Mark each method in the passed array as memoizable for the passed Klass. Backbone.Memoize will detect the appropriate Backbone.Collection and subscribe to add, change, and remove events. For classes other than Backbone.Collection it will only subscribe to change events. Also you can specify events with options. See example. If you set options == false, it will ignore all events => regular _.memoize behaviour.