react-helmet-async

What is react-helmet-async?

The react-helmet-async package is a reusable React component that manages changes to the document head, allowing developers to dynamically set the contents of the head section of the page, which includes the title, meta tags, and other elements. It is a thread-safe version of react-helmet that works well with server-side rendering.

What are react-helmet-async's main functionalities?

Setting the page title

This feature allows you to set the title of the page dynamically. The title tag inside the Helmet component will update the document's title when the component is rendered.

{"<Helmet><title>My Page Title</title></Helmet>"}

Managing meta tags

With this feature, you can manage meta tags such as the description, keywords, and others. This is particularly useful for SEO purposes and for providing metadata for social media platforms.

{"<Helmet><meta name='description' content='Page description' /></Helmet>"}

Adding link tags

This feature allows you to add link elements to the head, which can be used for defining canonical URLs, linking to stylesheets, or adding a favicon.

{"<Helmet><link rel='canonical' href='http://mysite.com/example' /></Helmet>"}

Adding script tags

You can dynamically add script tags to the head of the document, which is useful for including external JavaScript files or inline scripts.

{"<Helmet><script src='http://include.com/pathtojs.js' type='text/javascript' /></Helmet>"}

Other packages similar to react-helmet-async

react-helmet

This is the predecessor of react-helmet-async. It offers similar functionality for managing the document head, but it is not thread-safe and can have issues with server-side rendering in concurrent mode.

next-seo

A plugin for Next.js projects that provides a set of SEO components and helpers. It is similar to react-helmet-async but is specifically tailored for Next.js and includes additional SEO features.

react-meta-tags

A lightweight package for managing HTML meta tags in React applications. It is similar to react-helmet-async but with a simpler API and less overhead.

README

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.js.

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