JavaScript React seo Vue.js zero-configuration prerender HTML CSS static-site-generator ssr server-side-rendering
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Description

👻 Zero-configuration framework-agnostic static prerendering for SPAs

4.0K Stars 276 Forks MIT License 494 Commits 140 Opened issues

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Pre-renders a web app into static HTML. Uses Headless Chrome to crawl all available links starting from the root. Heavily inspired by prep and react-snapshot, but written from scratch. Uses best practices to get the best loading performance.

😍 Features

  • Enables SEO (Google, DuckDuckGo...) and SMO (Twitter, Facebook...) for SPAs.
  • Works out-of-the-box with create-react-app - no code-changes required.
  • Uses a real browser behind the scenes, so there are no issues with unsupported HTML5 features, like WebGL or Blobs.
  • Does a lot of load performance optimization. Here are details, if you are curious.
  • Does not depend on React. The name is inspired by
    react-snapshot
    but works with any technology (e.g., Vue).
  • npm package does not have a compilation step, so you can fork it, change what you need, and install it with a GitHub URL.

Zero configuration is the main feature. You do not need to worry about how it works or how to configure it. But if you are curious, here are details.

Basic usage with create-react-app

Install:

yarn add --dev react-snap

Change

package.json
:
"scripts": {
  "postbuild": "react-snap"
}

Change

src/index.js
(for React 16+):
import { hydrate, render } from "react-dom";

const rootElement = document.getElementById("root"); if (rootElement.hasChildNodes()) { hydrate(, rootElement); } else { render(, rootElement); }

That's it!

Basic usage with Preact

To do hydration in Preact you need to use this trick:

const rootElement = document.getElementById("root");
if (rootElement.hasChildNodes()) {
  preact.render(, rootElement, rootElement.firstElementChild);
} else {
  preact.render(, rootElement);
}

Basic usage with Vue.js

Install:

yarn add --dev react-snap

Change

package.json
:
"scripts": {
  "postbuild": "react-snap"
},
"reactSnap": {
  "source": "dist",
  "minifyHtml": {
    "collapseWhitespace": false,
    "removeComments": false
  }
}

Or use

preserveWhitespace: false
in
vue-loader
.

source
- output folder of webpack or any other bundler of your choice

Read more about

minifyHtml
caveats in #142.

Example: Switch from prerender-spa-plugin to react-snap

Caveats

Only works with routing strategies using the HTML5 history API. No hash(bang) URLs.

Vue uses the

data-server-rendered
attribute on the root element to mark SSR generated markup. When this attribute is present, the VDOM rehydrates instead of rendering everything from scratch, which can result in a flash.

This is a small hack to fix rehydration problem:

window.snapSaveState = () => {
  document.querySelector("#app").setAttribute("data-server-rendered", "true");
};

window.snapSaveState
is a callback to save the state of the application at the end of rendering. It can be used for Redux or async components. In this example, it is repurposed to alter the DOM, this is why I call it a "hack." Maybe in future versions of
react-snap
, I will come up with better abstractions or automate this process.

Vue 1.x

Make sure to use

replace: false
for root components

✨ Examples

⚙️ Customization

If you need to pass some options for

react-snap
, you can do this in your
package.json
like this:
"reactSnap": {
  "inlineCss": true
}

Not all options are documented yet, but you can check

defaultOptions
in
index.js
.

inlineCss

Experimental feature - requires improvements.

react-snap
can inline critical CSS with the help of minimalcss and full CSS will be loaded in a non-blocking manner with the help of loadCss.

Use

inlineCss: true
to enable this feature.

TODO: as soon as this feature is stable, it should be enabled by default.

⚠️ Caveats

Async components

Also known as code splitting, dynamic import (TC39 proposal), "chunks" (which are loaded on demand), "layers", "rollups", or "fragments". See: Guide To JavaScript Async Components

An async component (in React) is a technique (typically implemented as a higher-order component) for loading components on demand with the dynamic

import
operator. There are a lot of solutions in this field. Here are some examples:

It is not a problem to render async components with

react-snap
, the tricky part happens when a prerendered React application boots and async components are not loaded yet, so React draws the "loading" state of a component, and later when the component is loaded, React draws the actual component. As a result, the user sees a flash:
100%                    /----|    |----
                       /     |    |
                      /      |    |
                     /       |    |
                    /        |____|
  visual progress  /
                  /
0%  -------------/

Usually a code splitting library provides an API to handle it during SSR, but as long as "real" SSR is not used in react-snap - the issue surfaces, and there is no simple way to fix it.

  1. Use react-prerendered-component. This library holds onto the prerendered HTML until the dynamically imported code is ready.
import loadable from "@loadable/component";
import { PrerenderedComponent } from "react-prerendered-component";

const prerenderedLoadable = dynamicImport => { const LoadableComponent = loadable(dynamicImport); return React.memo(props => ( // you can use the .preload() method from react-loadable or react-imported-component` )); };

const MyComponent = prerenderedLoadable(() => import("./MyComponent"));

MyComponent
will use prerendered HTML to prevent the page content from flashing (it will find the required piece of HTML using an
id
attribute generated by
PrerenderedComponent
and inject it using
dangerouslySetInnerHTML
).
  1. The same approach will work with
    React.lazy
    , but
    React.lazy
    doesn't provide a prefetch method (
    load
    or
    preload
    ), so you need to implement it yourself (this can be a fragile solution).
const prefetchMap = new WeakMap();
const prefetchLazy = LazyComponent => {
  if (!prefetchMap.has(LazyComponent)) {
    prefetchMap.set(LazyComponent, LazyComponent._ctor());
  }
  return prefetchMap.get(LazyComponent);
};

const prerenderedLazy = dynamicImport => { const LazyComponent = React.lazy(dynamicImport); return React.memo(props => ( )); };

const MyComponent = prerenderedLazy(() => import("./MyComponent"));

  1. use
    loadable-components
    2.2.3 (current is >5). The old version of
    loadable-components
    can solve this issue for a "snapshot" setup:
import { loadComponents, getState } from "loadable-components";
window.snapSaveState = () => getState();

loadComponents() .then(() => hydrate(AppWithRouter, rootElement)) .catch(() => render(AppWithRouter, rootElement));

If you don't use babel plugin, don't forget to provide modules:

const NotFoundPage = loadable(() => import("src/pages/NotFoundPage"), {
  modules: ["NotFoundPage"]
});

loadable-components
were deprecated in favour of
@loadable/component
, but
@loadable/component
dropped
getState
. So if you want to use
loadable-components
you can use old version (
2.2.3
latest version at the moment of writing) or you can wait until
React
will implement proper handling of this case with asynchronous rendering and
React.lazy
.

Redux

See: Redux Server Rendering Section

// Grab the state from a global variable injected into the server-generated HTML
const preloadedState = window.__PRELOADED_STATE__;

// Allow the passed state to be garbage-collected delete window.__PRELOADED_STATE__;

// Create Redux store with initial state const store = createStore(counterApp, preloadedState || initialState);

// Tell react-snap how to save Redux state window.snapSaveState = () => ({ __PRELOADED_STATE__: store.getState() });

Caution: as of now, only basic "JSON" data types are supported: e.g.

Date
,
Set
,
Map
, and
NaN
won't be handled correctly (#54).

Third-party requests: Google Analytics, Mapbox, etc.

You can block all third-party requests with the following config:

"skipThirdPartyRequests": true

AJAX

react-snap
can capture all AJAX requests. It will store
json
requests in the domain in
window.snapStore[]
, where
 is the path of the request.

Use

"cacheAjaxRequests": true
to enable this feature.

This feature can conflict with the browser cache. See #197 for details. You may want to disable cache in this case:

"puppeteer": { "cache": false }
.

Service Workers

By default,

create-react-app
uses
index.html
as a fallback:
navigateFallback: publicUrl + '/index.html',

You need to change this to an un-prerendered version of

index.html
-
200.html
, otherwise you will see
index.html
flash on other pages (if you have any). See Configure sw-precache without ejecting for more information.

Containers and other restricted environments

Puppeteer (Headless Chrome) may fail due to sandboxing issues. To get around this, you may use:

"puppeteerArgs": ["--no-sandbox", "--disable-setuid-sandbox"]

Read more about puppeteer troubleshooting.

"inlineCss": true
sometimes causes problems in containers.

Docker + Alpine

To run

react-snap
inside
docker
with Alpine, you might want to use a custom Chromium executable. See #93 and #132.

Heroku

heroku buildpacks:add https://github.com/jontewks/puppeteer-heroku-buildpack.git
heroku buildpacks:add heroku/nodejs
heroku buildpacks:add https://github.com/heroku/heroku-buildpack-static.git

See this PR. At the moment of writing, Heroku doesn't support HTTP/2.

Semantic UI

Semantic UI is defined over class substrings that contain spaces (e.g., "three column"). Sorting the class names, therefore, breaks the styling. To get around this, use the following configuration:

"minifyHtml": { "sortClassName": false }

From version

1.17.0
,
sortClassName
is
false
by default.

JSS

Once JS on the client is loaded, components initialized and your JSS styles are regenerated, it's a good time to remove server-side generated style tag in order to avoid side-effects

https://github.com/cssinjs/jss/blob/master/docs/ssr.md

This basically means that JSS doesn't support

rehydration
. See #99 for a possible solutions.

react-router
v3

See #135.

userAgent

You can use

navigator.userAgent == "ReactSnap"
to do some checks in the app code while snapping—for example, if you use an absolute path for your API AJAX request. While crawling, however, you should request a specific host.

Example code:

const BASE_URL =
  process.env.NODE_ENV == "production" && navigator.userAgent != "ReactSnap"
    ? "/"
    : "http://xxx.yy/rest-api";

Alternatives

See alternatives.

Who uses it

| cloud.gov.au | blacklane | reformma | | ---------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------- | ------------------------------------------------------------------------------ |

Contributing

Report a bug

Please provide a reproducible demo of a bug and steps to reproduce it. Thanks!

Share on the web

Tweet it, like it, share it, star it. Thank you.

Code

You can also contribute to minimalcss, which is a big part of

react-snap
. Also, give it some stars.

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