jac

jac provides methods to reference asset urls using permanently cachable urls.

#jac jac provides methods to reference asset urls using permanently cachable urls.

It achieves this by using urls unique to each version of a given asset, and provides middleware to serve the asset with long cache durations.

#Usage jac middleware will handle asset file serving and asset url resolution

Install it using

npm install jac

The following example shows how to wire up jac

  • App code sets up the jac middleware
  • A JSON file stores the configuration for the jac middleware
  • A script updates the configuration file
var express = require('express')
  , config  = require('./config')
  , jac     = require('jac').create(config)
  , app     = express.createServer();
 
// Add middleware for all requests 
app.use(jac.middleware);
 
// Add view that resolves an image url 
app.get('/someview', function (reqres) {
  var jac = res.local('jac')        // returns jac view helper 
    , key = '/images/spacer.gif'    // matches config key 
    , url = jac.resolve(key);       // returns url with digest, handled by middleware 
 
  res.send(url);
});

The configuration file is updated using jac's digester and read by the app. Here's a sample config json file loaded by the app.

{
  // required - files served by jac 
  assets: [{
    fullPath: require('path').resolve(__dirname, './public/images/spacer.gif'),
    key:      '/images/spacer.gif',
    route:    '/images/spacer.gif?b64Digest'
  }],
 
  // optional - cache control max age in seconds (default 2 weeks) 
  maxAge: 5443200
}

The update script runs the digester against the files specified in configuration and updates the files key in the configuration file. This script can be run from package.json's scripts section after install.

jac --config ./config.json

Alternatively, the digester can be wired up manually

var path   = './config'
  , config = require(path)
  , digest = require('jac').digest;
 
function save (errassets) {
  if (err) throw err;
 
  config.assets = assets;
  fs.writeFile(path, JSON.stringify(config, null, 2));
}
 
digest(config, save);

This version of jac is compatible with express 2.5. It depends on res.local() to get and set the view local jac.img via middleware.

To support production usage with the best performance, it is required that a pre-processing step be executed to generate the image file digests stored in configuration.

jac --config ./config.json

It is recommended that the config file already exist, and the config file used by the app always be updated before deploying to production. This can be automated using package.json's scripts section after install.

{
  "name": "myproject",
  "dependencies": {
    "jac": "latest"
  },
  "scripts": {
    "postinstall": "./node_modules/jac/bin/jac"
  }
}

Running Tests

To run the test suite first invoke the following command within the repo, installing the development dependencies:

npm install

then run the tests:

npm test

License

(The MIT License)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.