script-ext-html-webpack-plugin/README.md

Script Extension for HTML Webpack Plugin
========================================
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Enhances [html-webpack-plugin](https://github.com/ampedandwired/html-webpack-plugin)
functionality with different deployment options for your scripts including:
- [`async`](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script#Attributes) attribute;
- [`defer`](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script#Attributes) attribute;
- [`type="module"`](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script#Attributes) attribute;
- inlining;
- [`preload`](https://www.w3.org/TR/preload/) resource hint;
- [`prefetch`](https://www.w3.org/TR/resource-hints/#dfn-prefetch) resource hint

This is an extension plugin for the [webpack](http://webpack.github.io) plugin [html-webpack-plugin](https://github.com/ampedandwired/html-webpack-plugin) - a plugin that simplifies the creation of HTML files to serve your webpack bundles.

The raw [html-webpack-plugin](https://github.com/ampedandwired/html-webpack-plugin) incorporates all webpack-generated javascipt as synchronous`<script>` elements in the generated html.  This plugin allows you to:
- add attributes to these elements;
- inline the code in the elements;
- add asynchronous scripts to prefetch and preload resource hints.

Installation
------------
You must be running webpack (1.x or 2.x) )on node 4+.

Install the plugin with npm:
```shell
$ npm install --save-dev script-ext-html-webpack-plugin
```

You may see an `UNMET PEER DEPENDENCY` warning for webpack.

This is fine; in testing, we dynamically download multiple versions of webpack (via the [dynavers](https://github.com/numical/dynavers) module).


Basic Usage
-----------
Add the plugin to your webpack config as follows: 

```javascript
plugins: [
  new HtmlWebpackPlugin(),
  new ScriptExtHtmlWebpackPlugin()
]  
```
The above configuration will actually do nothing due to the configuration defaults. Some more useful scenarios:

All scripts set to `async`:
```javascript
plugins: [
  new HtmlWebpackPlugin(),
  new ScriptExtHtmlWebpackPlugin({
    defaultAttribute: 'async'
  })
]  
```

All scripts set to `async` except 'first.js' which is sync:
```javascript
plugins: [
  new HtmlWebpackPlugin(),
  new ScriptExtHtmlWebpackPlugin({
    sync: 'first.js',
    defaultAttribute: 'async'
  })
]  
```

Configuration offers much more complex options:

Configuration
-------------
You must pass a hash of configuration options to the plugin to cause the addition of attributes:
- `inline`: a __script matching pattern__ defining scripts that should be inlined in the html (default: `[]`);
- `sync`: a  __script matching pattern__ defining script names that should have no attribute (default: `[]`);
- `async`: a __script matching pattern__ defining script names that should have an `async` attribute (default: `[]`);
- `defer`: a __script matching pattern__ defining script names that should have a `defer` attribute (default: `[]`);
- `defaultAttribute`: `'sync' | 'async' | 'defer'` The default attribute to set - `'sync'` actually results in no attribute (default: `'sync'`);
- `module`: a __script matching pattern__ defining script names that should have a
`type="module"` attribute (default: `[]`);
- `preload`: a __script matching pattern__ defining scripts that should have accompanying preload resource hints (default: `[]`);
- `prefetch`: a __script matching pattern__ defining scripts that should have accompanying prefetch resource hints (default: `[]`);

A __script matching pattern__ matches against a script's name.  It can be one of:
- a `String`-  matches if it is a substring of the script name;
- a `RegExp`;
- an array of `String`'s and/or `RegExp`'s - matches if any one element matches;
- a hash with property `test` with a value of one of the above.

In more complicated use cases it may prove difficult to ensure that the pattern matching for different attributes are mutually exclusive.  To prevent confusion, the plugin operates a simple precedence model:

1. if a script name matches the`inline` script matching pattern, it will be inlined;

2. if a script name matches the `sync` script matching pattern, it will have no attribute, *unless* it matched condition 1;

3. if a script name the `async` script matching pattern, it will have the `async` attribute, *unless* it matched conditions 1 or 2;

4. if a script name matches the `defer` script matching pattern, it will have the `defer` attribute, *unless* it matched conditions 1, 2 or 3;

5. if a script name does not match any of the previous conditions, it will have the `defaultAttribute' attribute.

The `module` attribute is independent of conditions 2-5, but will be ignored if the script isinlined.

The `preload` and `prefetch` configuration also have allow an additional property in the hash form that can be passed to include dynamically loaded (asynchronous) scripts.  This property is `chunks` and can have one of the following `String` values:
- `initial`: default behaviour, no asynchronour scripts;
- `async`: only asynchronouse scripts;
- `all`: all scripts
Note that you must still supply a `test` __script matching pattern__ which is also applied when selecting scripts.

Some Examples:

All scripts with 'important' in their name are sync and all others set to `defer`:
```javascript
plugins: [
  new HtmlWebpackPlugin(),
  new ScriptExtHtmlWebpackPlugin({
    sync: 'important'
    defaultAttribute: 'defer'
  })
]  
```

Alternatively, using a regular expression:
```javascript
plugins: [
  new HtmlWebpackPlugin(),
  new ScriptExtHtmlWebpackPlugin({
    sync: /important/,
    defaultAttribute: 'defer'
  })
]  
```

All scripts with 'mod' in their name are async and type 'module', all others are sync (no explicit setting for this as it is the default):
```javascript
plugins: [
  new HtmlWebpackPlugin(),
  new ScriptExtHtmlWebpackPlugin({
    async: 'mod',
    module: 'mod'
  })
]  
```

Script 'startup.js' is inlined whilst all other scripts are async and preloaded:
```javascript
plugins: [
  new HtmlWebpackPlugin(),
  new ScriptExtHtmlWebpackPlugin({
    inline: 'startup',
    preload: /\.js$/,
    defaultAttribute: 'async'
  })
]  
```

All asynchronous scripts are added as `preload` resource hints.  All other scripts are `async`:
```javascript
plugins: [
  new HtmlWebpackPlugin(),
  new ScriptExtHtmlWebpackPlugin({
    async: /\.js$/
    preload: {
      test: /\.js$/,
      chunks: 'async'
    }
  })
]  
```



And so on, to craziness:
```javascript
plugins: [
  new HtmlWebpackPlugin(),
  new ScriptExtHtmlWebpackPlugin({
    inline: 'startup',  
    sync: [/imp(1|2){1,3}}/, 'initial'],
    defer: ['slow', /big.*andslow/],
    module: [/^((?!sync).)*/, 'mod'],
    prefetch: 'indirectly-referenced.js',
    defaultAttribute: 'async'
  })
]  
```

Any problems with real-world examples, just raise an issue.  


A Note on Script Names
----------------------
In the above examples the actual script names are used to select the deployment option.  You may not wish to couple asset names to your deployment like this.  Instead you can use [Webpack's entry configuration](https://webpack.js.org/concepts/entry-points/#object-syntax) to create aliases that the plugin will then use for its pattern matching. Your `webpack.config.js` will look something like this:
```javascript
entry: {
  a: path.join(__dirname, 'lib/myFunctions.js'),
  b: path.join(__dirname, 'lib/otherFunctions.js'),
  c: path.join(__dirname, 'lib/criticalFuntions.js')
},
output: {
  ...
  filename: '[name].js'
}
plugins: [
  new HtmlWebpackPlugin(),
  new ScriptExtHtmlWebpackPlugin({
    inline: ['c'],  
    defer: ['a', 'b']
  })
]  
```


Inlining
--------
Several notes and caveats apply:
* This feature is for `<script>`'s only. If you wish to inline css please see the sister plugin
[style-ext-html-webpack-plugin](https://github.com/numical/style-ext-html-webpack-plugin).
* Even the simplest script will be wrapped with webpack boilerplate; ensure you minify your javascript if you want your output html to be legible!
* Hot replacement of inlined scripts will only work if caching is [switched off](https://github.com/ampedandwired/html-webpack-plugin#configuration) for html-webpack-plugin:
```javascript
plugins: [
    new HtmlWebpackPlugin({
      cache: false
    }),
    new ScriptExtHtmlWebpackPlugin({
      inline: ['myinlinedscript.js']
    })
]
```
* An alternative approach, based on jade templates is illustrated in the [HtmlWebpackPlugin inline example](https://github.com/ampedandwired/html-webpack-plugin/tree/master/examples/inline).


Resource Hints
--------------
In most cases, modern browsers will intelligently preload referenced script assets.
However if you wish, this plugin can add resource hint elements to the `<head>` element of the form:
```html
<link rel="[preload|prefetch]" href="[scriptname]" as="script">
```
Use the `preload` and `prefetch` configuration options.

Where `preload` and `prefetch` patterns overlap, `preload` takes precedence.

Notes:
- for more on resource hints, see the [`w3c`](https://www.w3.org/TR/resource-hints) definition;  
- for a more complete solution that allows the preloading\fetching of assets other than scripts, see the [resource-hints-webpack-plugin](https://github.com/jantimon/resource-hints-webpack-plugin).



Change History
--------------

v1.7.x
* adds asynchronous script resource hints

v1.6.x
* works with webpack 2.2.1
* enhanced API (no need to use array), fully backwardly compatible
* refactor in preparation for v2

v1.5.x
* added resource hints
* works with webpack 2.2.0

v1.4.x
* updated internal mechanism to use new(ish) [HtmlWebpackPlugin event](https://github.com/ampedandwired/html-webpack-plugin#events)
* improved test mechanism and enhanced test coverage
* added support for `publicPath` for inline scripts (thanks @JustAboutJeff)
* works with 'webpack -p' (thanks @brandongoode)

v1.3.x
* added `type="text/javascript"` by default, in response to [Safari 9.1.1 bug](https://github.com/ampedandwired/html-webpack-plugin/issues/309)
* removed experimental status of inline option
* added weback 2.2.x beta support

v1.2.x
* added inline option

v1.1.x
* added `type="module"` option

v1.0.x
* initial release