Static file asset revisioning through content hashing

If you haven't used grunt before, be sure to check out the Getting Started guide.

From the same directory as your project's Gruntfile and package.json, install this plugin with the following command:

npm install grunt-rev --save-dev

Once that's done, add this line to your project's Gruntfile:

grunt.loadNpmTasks('grunt-rev');

If the plugin has been installed correctly, running grunt --help at the command line should list the newly-installed plugin's task or tasks. In addition, the plugin should be listed in package.json as a devDependency, which ensures that it will be installed whenever the npm install command is run.

Use the rev task together with yeoman/grunt-usemin for cache busting of static files in your app. This allows them to be cached forever by the browser.

In your project's Gruntfile, add a section named rev to the data object passed into grunt.initConfig().

grunt.initConfig({
  rev: {
    options: {
      encoding: 'utf8',
      algorithm: 'md5',
      length: 8
    },
    assets: {
      files: [{
        src: [
          'img/**/*.{jpg,jpeg,gif,png}',
          'fonts/**/*.{eot,svg,ttf,woff}'
        ]
      }]
    }
  },
})

Type: String Default value: 'utf8'

The encoding of the file contents.

Type: String Default value: 'md5'

algorithm is dependent on the available algorithms supported by the version of OpenSSL on the platform. Examples are 'sha1', 'md5', 'sha256', 'sha512', etc. On recent releases, openssl list-message-digest-algorithms will display the available digest algorithms.

Type: Number Default value: 8

The number of characters of the file content hash to prefix the file name with.

This will rename app.js and app.css with an 8 character long hash prefix. For example js/9becff3a.app.js and css/ae35dd05.app.css. The hash value depends on the file contents.

grunt.initConfig({
  rev: {
    files: {
      src: ['scripts/app.js', 'css/app.css']
    }
  }
})

Change the algorithm or length to style the generated asset file names. Note that the usemin companion task requires at least one anycase hexadecimal character to prefix the file name.

grunt.initConfig({
  rev: {
    options: {
      algorithm: 'sha1',
      length: 4
    },
    files: {
      src: ['**/*.{js,css,png,jpg}']
    }
  }
})

In lieu of a formal styleguide, take care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint and test your code using grunt.

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