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Mini Shell
Mini Shell
# react-helmet-async
[](https://circleci.com/gh/staylor/react-helmet-async)
[Announcement post on Times Open blog](https://open.nytimes.com/the-future-of-meta-tag-management-for-modern-react-development-ec26a7dc9183)
This package is a fork of [React Helmet](https://github.com/nfl/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:
```javascript
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.
```javascript
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:
```javascript
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.
```javascript
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:
```javascript
<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:
```javascript
<html>
<head>
${helmet.title.toString()}
${helmet.priority.toString()}
${helmet.meta.toString()}
${helmet.link.toString()}
${helmet.script.toString()}
</head>
...
</html>
```
Will result in:
```html
<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](./src/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:
```js
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
Zerion Mini Shell 1.0