Backbone fetch cache

A Backbone plugin to cache calls to Backbone.Model.prototype.fetch and Backbone.Model.prototype.fetch in memory and localStorage.

How it works

This plugin intercepts calls to fetch and stores the results in a cache object (Backbone.fetchCache._cache). If fetch is called with { cache: true } in the options and the URL has already been cached the AJAX call will be skipped.

The local cache is persisted in localStorage if available for faster initial page loads.

The prefill option allows for models and collections to be filled with cache data just until the fetch operations are complete -- a nice way to make the app feel snappy on slower connections.

What's wrong with browser caching for AJAX responses?

Nothing. This plugin is primarily for working with an API where you don't have control over response cache headers.

Usage

Add the script to the page after backbone.js has been included:

<script src="/path/to/backbone.js"></script>
<script src="/path/to/backbone.fetch-cache.js"></script>

Options

cache

Calls to modelInstance.fetch or collectionInstance.fetch will be fulfilled from the cache (if possible) when cache: true is set in the options hash:

myModel.fetch({ cache: true });
myCollection.fetch({ cache: true });

---

prefill

This option allows the model/collection to be populated from the cache immediately and then be updated once the call to fetch has completed. The initial cache hit calls the prefillSuccess callback and then the AJAX success/error callbacks are called as normal when the request is complete. This allows the page to render something immediately and then update it after the request completes. (Note: the prefillSuccess callback will not fire if the data is not found in the cache.)

myModel.fetch({
  prefill: true,
  prefillSuccess: someCallback, // Fires when the cache hit happens
  success: anotherCallback // Fires after the AJAX call
});

myCollection.fetch({
  prefill: true,
  prefillSuccess: someCallback, // Fires when the cache hit happens
  success: anotherCallback // Fires after the AJAX call
});

This option can be used with the promises interface like so (note: the progress event will not fire if the data is not found in the cache.):

var modelPromise = myModel.fetch({ prefill: true });
modelPromise.progress(someCallback); // Fires when the cache hit happens
modelPromise.done(anotherCallback); // Fires after the AJAX call

var collectionPromise = myModel.fetch({ prefill: true });
collectionPromise.progress(someCallback); // Fires when the cache hit happens
collectionPromise.done(anotherCallback); // Fires after the AJAX call

---

expires

Cache vales expire after 5 minutes by default. You can adjust this by passing expires: <seconds> to the fetch call. Set to false to never expire:

myModel.fetch({ cache: true, expires: 60000 });
myCollection.fetch({ cache: true, expires: 60000 });

// These will never expire
myModel.fetch({ cache: true, expires: false });
myCollection.fetch({ cache: expires: false });

---

localStorage

By default the cache is persisted in localStorage (if available). Set Backbone.fetchCache.localStorage = false to disable this:

Backbone.fetchCache.localStorage = false;

Tests

You can run the tests by cloning the repo, installing the dependencies and running grunt jasmine:

$ npm install
$ grunt jasmine

To see the tests in a browser, run:

$ grunt jasmine-server

The default grunt task runs tests and lints the code.

$ grunt

Changelog

• v0.1.1: Add prefetch option.