prerenderer-webpack-plugin

Prerenderer Webpack Plugin

Fast, flexible prerendering for sites and SPAs built with webpack.

About prerenderer-webpack-plugin

The goal of this plugin is to provide a simple prerendering solution that is easily extensible and useble for any site or single-page-app built with webpack.

It's implemented as a webpack wrapper for prerenderer. For more up-to-date and complete documentation, see that repository.

Plugins for other task runners and build systems are planned.

Example Usage (webpack.config.js)

const path = require('path')
const PrerendererWebpackPlugin = require('prerenderer-webpack-plugin')
const ChromeRenderer = PrerendererWebpackPlugin.ChromeRenderer

module.exports = {
  plugins: [
    ...
    new PrerendererWebpackPlugin({
      // Required - The path to the webpack-outputted app to prerender.
      staticDir: path.join(__dirname, 'dist'),
      // Required - Routes to render.
      routes: [ '/', '/about', '/some/deep/nested/route' ],

      // Optional - This is the default.
      renderer: new ChromeRenderer({
        // If this is omitted, ChromeRenderer will *attempt* to find a valid installed version based on your platform. No promises.
        command: 'start chrome' // Windows
        // More optional renderer arguments.
      })
    })
  ]
}

Now, if you're not familiar with the concept of prerendering, you might predictably ask...

What is Prerendering?

Recently, SSR (Server Side Rendering) has taken the JavaScript front-end world by storm. The fact that you can now render your sites and apps on the server before sending them to your clients is an absolutely revolutionary idea (and totally not what everyone was doing before JS client-side apps got popular in the first place...)

However, the same criticisms that were valid for the PHP, ASP, JSP, and the likes sites of yore are valid for server-side rendering today. It's slow, breaks fairly easily, and is difficult to implement properly.

Thing is, despite what everyone might be telling you, you probably don't need SSR. You can get almost all the advantages of it (without the disadvantages) by using prerendering. Prerendering is basically firing up a headless browser, loading your app's routes, and saving the results to a static HTML file. You can then serve it with whatever static-file-serving solution you were using previously. It just works with HTML5 navigation and the likes. No need to change your code or add server-side rendering workarounds.

In the interest of transparency, there are some use-cases where prerendering might not be a great idea.

• Tons of routes - If your site has hundreds or thousands of routes, prerendering will be really slow. Sure you only have to do it once per update, but it could take ages. Most people don't end up with thousands of static routes, but just in-case...
• Dynamic Content - If your render routes that have content that's specific to the user viewing it or other dynamic sources, you should make sure you have placeholder components that can display until the dynamic content loads on the client-side. Otherwise it might be a tad weird.

Available Renderers

• Chromium / Google Chrome Headless over RDP (builtin) - PrerendererWebpackPlugin.ChromeRenderer

Documentation

Plugin Options

Option	Type	Required?	Default	Description
staticDir	String	Yes	None	The root path to serve your app from.
outputDir	String	No	staticDir	The path to output the rendered app to.
routes	Array:String	Yes	[]	Routes to prerender.
server	Object	No	None	App server configuration options (See below)
renderer	Renderer Instance or Object	No	new ChromeRenderer()	The renderer you'd like to use to prerender the app. It's recommended that you specify this, but if not it will attempt to start ChromeRenderer.

Server Options

Option	Type	Required?	Default	Description
port	Integer	No	First free port after 8000	The port for the app server to run on.

ChromeRenderer Options

Option	Type	Required?	Default	Description
inject	Object	No	None	An object to inject into the global scope of the rendered page before it finishes loading. Must be JSON.stringifiy-able. The property injected to is window['__PRERENDER_INJECTED'] by default.
injectProperty	String	No	'__PRERENDER_INJECTED'	The property to mount inject to during rendering.
renderAfterDocumentEvent	String	No	None	Wait to render until the specified event is fired on the document. (You can fire an event like so: document.dispatchEvent(new Event('custom-render-trigger'))
renderAfterElementExists	String (Selector)	No	None	Wait to render until the specified element is detected using document.querySelector
renderAfterTime	Integer (Milliseconds)	No	None	Wait to render until a certain amount of time has passed.
maxLaunchRetries	Integer	No	5	Max amount of times to try and start the render program before erroring out.
port	Integer	No	Auto-detect available port	The port to run Chrome's RDP on.
command	String	No (Recommended)	Auto-detect	The command to use to start Chrome or Chromium. Auto-detection is unreliable, so I'd recommend setting it.
arguments	Array:String	No	None	Additional arguments to pass to Chrome.

Caveats

• For obvious reasons, prerenderer only works for SPAs that route using the HTML5 history API. index.html#/hash/route URLs will unfortunately not work.
• Whatever client-side rendering library you're using should be able to at least replace any server-rendered content or diff with it.
  • For Vue.js 1 use replace: false on root components.
  • For Vue.js 2 Ensure your root component has the same id as the prerendered element it's replacing. Otherwise you'll end up with duplicated content.

License (MIT)

Copyright (c) 2017 Joshua Michael Bemenderfer

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.

Credits

• Originally ported from prerender-spa-plugin by Chris Fritz. Thanks Chris!

Maintainers

Joshua Bemenderfer