react-helmet-async
Announcement post on Times Open blog
This package is a fork of React Helmet.
<Helmet> usage is synonymous, but server and client now requires <HelmetProvider> to encapsulate state per request.
react-helmet relies on react-side-effect, which is not thread-safe. If you are doing anything asynchronous on the server, you need Helmet to encapsulate data on a per-request basis, this package does just that.
Usage
New is 1.0.0: No more default export! import { Helmet } from 'react-helmet-async'
The main way that this package differs from react-helmet is that it requires using a Provider to encapsulate Helmet state for your React tree. If you use libraries like Redux or Apollo, you are already familiar with this paradigm:
import React from 'react';
import ReactDOM from 'react-dom';
import { Helmet, HelmetProvider } from 'react-helmet-async';
const app = (
<HelmetProvider>
<App>
<Helmet>
<title>Hello World</title>
<link rel="canonical" href="https://www.tacobell.com/" />
</Helmet>
<h1>Hello World</h1>
</App>
</HelmetProvider>
);
ReactDOM.hydrate(
app,
document.getElementById(‘app’)
);
On the server, we will no longer use static methods to extract state. react-side-effect
exposed a .rewind() method, which Helmet used when calling Helmet.renderStatic(). Instead, we are going
to pass a context prop to HelmetProvider, which will hold our state specific to each request.
import React from 'react';
import { renderToString } from 'react-dom/server';
import { Helmet, HelmetProvider } from 'react-helmet-async';
const helmetContext = {};
const app = (
<HelmetProvider context={helmetContext}>
<App>
<Helmet>
<title>Hello World</title>
<link rel="canonical" href="https://www.tacobell.com/" />
</Helmet>
<h1>Hello World</h1>
</App>
</HelmetProvider>
);
const html = renderToString(app);
const { helmet } = helmetContext;
// helmet.title.toString() etc…
Streams
This package only works with streaming if your <head> data is output outside of renderToNodeStream().
This is possible if your data hydration method already parses your React tree. Example:
import through from 'through';
import { renderToNodeStream } from 'react-dom/server';
import { getDataFromTree } from 'react-apollo';
import { Helmet, HelmetProvider } from 'react-helmet-async';
import template from 'server/template';
const helmetContext = {};
const app = (
<HelmetProvider context={helmetContext}>
<App>
<Helmet>
<title>Hello World</title>
<link rel="canonical" href="https://www.tacobell.com/" />
</Helmet>
<h1>Hello World</h1>
</App>
</HelmetProvider>
);
await getDataFromTree(app);
const [header, footer] = template({
helmet: helmetContext.helmet,
});
res.status(200);
res.write(header);
renderToNodeStream(app)
.pipe(
through(
function write(data) {
this.queue(data);
},
function end() {
this.queue(footer);
this.queue(null);
}
)
)
.pipe(res);
Usage in Jest
While testing in using jest, if there is a need to emulate SSR, the following string is required to have the test behave the way they are expected to.
import { HelmetProvider } from 'react-helmet-async';
HelmetProvider.canUseDOM = false;
Prioritizing tags for SEO
It is understood that in some cases for SEO, certain tags should appear earlier in the HEAD. Using the prioritizeSeoTags flag on any <Helmet> component allows the server render of react-helmet-async to expose a method for prioritizing relevant SEO tags.
In the component:
<Helmet prioritizeSeoTags>
<title>A fancy webpage</title>
<link rel="notImportant" href="https://www.chipotle.com" />
<meta name="whatever" value="notImportant" />
<link rel="canonical" href="https://www.tacobell.com" />
<meta property="og:title" content="A very important title"/>
</Helmet>
In your server template:
<html>
<head>
${helmet.title.toString()}
${helmet.priority.toString()}
${helmet.meta.toString()}
${helmet.link.toString()}
${helmet.script.toString()}
</head>
...
</html>
Will result in:
<html>
<head>
<title>A fancy webpage</title>
<meta property="og:title" content="A very important title"/>
<link rel="canonical" href="https://www.tacobell.com" />
<meta name="whatever" value="notImportant" />
<link rel="notImportant" href="https://www.chipotle.com" />
</head>
...
</html>
A list of prioritized tags and attributes can be found in constants.ts.
Usage without Context
You can optionally use <Helmet> outside a context by manually creating a stateful HelmetData instance, and passing that stateful object to each <Helmet> instance:
import React from 'react';
import { renderToString } from 'react-dom/server';
import { Helmet, HelmetProvider, HelmetData } from 'react-helmet-async';
const helmetData = new HelmetData({});
const app = (
<App>
<Helmet helmetData={helmetData}>
<title>Hello World</title>
<link rel="canonical" href="https://www.tacobell.com/" />
</Helmet>
<h1>Hello World</h1>
</App>
);
const html = renderToString(app);
const { helmet } = helmetData.context;
License
Licensed under the Apache 2.0 License, Copyright © 2018 Scott Taylor
