Scout

Developer README

This repository provides a Node module that can be used to generate a "scout" file for a client-side JavaScript application.

Requirements

To use this project, it is assumed you already have an environment running Node 5.

The application module is written using ES6. In order to use the source you may need to provide your own transpiler, depending on your supported browsers.

We also take advantage of some built-ins that you may need to polyfill:

• Promise: http://caniuse.com/#feat=promises

Roadmap and Issues

See the issues page for details on current development and future plans. If there is scout file functionality that your project needs and is not provided currently, please open an issue. Bug reports are also appreciated.

Overview

A scout file is a small JavaScript file that serves as a loader for a client- side JavaScript application. The scout file must always be less than 14k when minified and gzipped. The scout file should have a short TTL, so changes will take effect quickly; the resources it loads should have versioned URLs, allowing them to have long TTLs.

Read more about scout files and deploying JavaScript applications.

The scout file's key responsibilities are:

• Load the core application resources
• Queue calls to render the core application until the core application is loaded
• Provide a way for the core application to access configuration information
• Provide a way for the core application to respond to any queued render calls
• Provide a way for the core application to redefine render behavior for future calls

This project uses webpack to generate the built scout file. It allows client-side JavaScript applications to specify the functionality required in their scout file and provide any code that is unique to their application that should be included in the scout file. It also provides loaders for common tasks, such as using a JSON file as a source, or inlining CSS. See below for more details about loaders

Example

To try an example:

• Clone this repo:

git clone https://github.com/bazaarvoice/scoutfile.git

• Copy the files from the example directory of the repo:

cd scoutfile
cp -r example ../scout-example

• Run the example:

cd ../scout-example
npm install
node generator.js

• Run the example Grunt task (make sure to npm install -g grunt-cli first if you don't already have the Grunt CLI installed):

grunt scoutfile

Usage

You will need to npm install the scoutfile module and save it to your project's dependencies:

npm install --save scoutfile

Check the repo for the latest stable version, and modify the command above as required.

You can now write your application's portion of the scout file. The example below shows an application that includes modules provided by the scout project (see Including common functionality via modules), as well as a JSON resource (see Including non-JS-resources).

var App = require('scoutfile/lib/browser/application');
var loader = require('scoutfile/lib/browser/loader');
 
var config = require('json!./config.json');
 
var MyApp = App('MyApp');
 
MyApp.config = config;
MyApp.loadScript = loader.loadScript;
 
loader.loadScript(config.appJS);
loader.loadStyleSheet(config.appCSS);

Including common functionality via modules

This project provides modules for common tasks, such as reading and writing cookies; loading JavaScript and CSS; and queueing JavaScript calls from the host site until the core application resources arrive. Learn more about the modules provided by this project.

Including non-JS resources

The scout project provides access to several Webpack loaders. These assist with common tasks such as embedding a JSON file into the built scout file; loading CSS into the built scout file; loading templates into the built scout file; and other tasks. The following loaders are currently provided:

• Handlebars
• JSON
• Raw
• Sass
• Yaml
• CSS
• File

If your project would benefit from a loader that is not listed here, please fork this repository, create a branch, add the loader via npm install --save, and then open a pull request explaining the need.

Generating a scout file

Via Node

The following code will log the generated scout file as a string:

var scout = require('scoutfile');
scout.generate({
  appModules: [
    {
      name: 'MyApp',
      path: './app/scripts/scout/main.js'
    }
  ],
 
  // Specify `pretty` to get un-uglified output.
  pretty: true
}).then(function (scout) {
  console.log(scout);
});

Via Grunt

This project also provides a Grunt task. To use it, first, load the Grunt task in your Gruntfile.js:

grunt.loadNpmTasks('scoutfile');

This creates a scoutfile Grunt multitask. You can configure the task as follows, providing the source modules and the destination for each multitask configuration:

grunt.initConfig({
  // ...
  scoutfile: {
    server : {
      src : [
        {
          name : 'MyApp',
          path : './app/scripts/scout/main.js'
        }
      ],
      dest : '.tmp/scripts/scout.js',
 
      // Specify `pretty` to get un-uglified code
      pretty : true
    },
    test : {
      src : [
        {
          name : 'MyApp',
          path : './app/scripts/scout/main.js'
        }
      ],
      dest : '.tmp/scripts/scout.js'
    }
  },
  // ...
});

To use the task, you can now run:

grunt scoutfile:server

Controlling the Output

Specifying a "namespace"

By default, the scout will create window.APP, and use that as its namespace if it needs to expose anything globally. This namespace can be accessed via the lib/browser/namespace module. You can specify a different namespace by setting the namespace property of the configuration that you pass to the generator.

Specifying a namespace when using the scout module:

var scout = require('scoutfile');
scout.generate({
  appModules: [
    {
      name: 'MyApp',
      path: './app/scripts/scout/main.js'
    }
  ],
 
  // Override the default `APP` namespace
  namespace: 'APPLICATION',
 
  // Specify `pretty` to get un-uglified output.
  pretty: true
}).then(function (scout) {
  console.log(scout);
});

Specifying a namespace for a Grunt task:

grunt.initConfig({
  // ...
  scoutfile: {
    server : {
      src : [
        {
          name : 'MyApp',
          path : './app/scripts/scout/main.js'
        }
      ],
      dest : '.tmp/scripts/scout.js',

      // Override the default `APP` namespace
      namespace: 'APPLICATION',

      // Specify `pretty` to get un-uglified code
      pretty : true
    }
  },
  // ...
});

Using build flags

You can also define flags that can be used to control build output; for example, you could define a flag DEBUG that you could then use to only execute certain code when the flag is true:

if (DEBUG) {
  doSomething();
}
else {
  doSomethingElse();
}

If a flag is false for a certain build configuration, and the pretty option is not true, then Uglification will include dead code removal. So, for example, if the DEBUG flag was set to false for a certain build configuration, the above code would be reduced to:

doSomethingElse();

To specify flags, add a flags property to the config you provide to the generator (or the config for each grunt task). The value of this property should be an object, such as:

flags : {
  DEBUG : true
}

If you are using a flag in your application's scout file code, note that it's important to define it for all build configurations -- not just for the build configuration for which it is true.

Read more about flags and the Webpack DefinePlugin here.

Including configuration information

To specify configuration data that should be available within the generated scout file, add an appConfig property to the config you provide to the generator (or the config for each grunt task).

appConfig : {
  reviews : true,
  comments : false,
  customerName : 'atticus'
}

The value you provide here should be an object that can be serialized using JSON.stringify. See the modules documentation for details on how to access this data via the appConfig module.

Including a banner

To specify one or more "banners" to appear at the top of your file, add a banner property to the config you provide to the generator (or the config for each grunt task).

banner : {
  content : 'Copyright 2015 Bazaarvoice. All rights reserved.'
}

By default, a banner will be inserted as a comment at the top of the generated file. You can provide an options property to insert raw, uncommented content instead:

banner : {
  content : '"version:697-test-8e037c82-e49a-4136-ade1-fbe08c281a24";',
  options : {
    raw : true
  }
}

You can also provide an array of banner objects:

banner : [
  {
    content : '"version:697-test-8e037c82-e49a-4136-ade1-fbe08c281a24";',
    options : {
      raw : true
    }
  },
  {
    content : 'Copyright 2015 Bazaarvoice. All rights reserved'.
  }
];

Advanced Webpack configuration and source maps

By passing in Webpack configuration options to the generator, you can override any of the default Webpack configuration that is constructed when generating a scout file. Note that this can absolutely break things, for example if you provide your own plugins array that includes plugins used by this library.

A more common use case is to request a source map to be constructed:

var scout = require('scoutfile');
scout.generate({
  appModules: [
    {
      name: 'MyApp',
      path: './app/scripts/scout/main.js'
    }
  ],

  // Specify `pretty` to get un-uglified output.
  pretty: true,

  // Specify overridden Webpack options.
  webpackOptions: {
    // Create a source map file main.js.map in addition to the scout file.
    devtool: 'source-map'
  }
}).then(function (sources) {
  // When requesting a source map file in addition to a scout file, an array
  // is returned.
  console.log('Scout: ' + sources[0]);
  console.log('Source map: ' + sources[1]);
});

If using the grunt task, a sourceMapDest configuration property must be provided in addition to dest if the source map is generated as a separate file:

grunt.initConfig({
  // ...
  scoutfile: {
    server : {
      src : [
        {
          name : 'MyApp',
          path : './app/scripts/scout/main.js'
        }
      ],
      dest : '.tmp/scripts/scout.js',
      sourceMapDest : '.tmp/scripts/scout.js.map'

      // Override the default `APP` namespace
      namespace: 'APPLICATION',

      // Specify `pretty` to get un-uglified code
      pretty : true,

      // Specify overridden Webpack options.
      webpackOptions: {
        // Create a source map file that will be written to sourceMapDest.
        devtool: 'source-map'
      }
    }
  },
  // ...
});

Troubleshooting

loader timeout

Understanding the loader module is critical to the usage of this repository. The default timeout is sufficient for common usage, but may not be large enough for environments where load times will be much slower than anticipated, such as slow mobile networks, dial-up connection, use of tunneling Selenium test services such as BrowserStack and Sauce Labs, and so forth. Older browsers such as IE8 may obfuscate timeout problems with other errors, making it difficult to debug such issues.

If you experience any issues with application load timeouts, review the documentation on the timeout option and experiment with larger timeout values.