React

FAST can be used in React applications. Let's take a look at how you can set up a project, starting from scratch.

Setting up the React project#

First, you'll need to make sure that you have Node.js >= 8.2 and npm >= 5.6 installed. You can learn more and download that on the official site.

With Node.js installed, you can use create-react-app to create a new React project.

npx create-react-app fast-app

Configuring packages#

Next, we'll install the FAST packages, along with supporting libraries. To do that, run this command from your new project folder:

npm install --save @microsoft/fast-components @microsoft/fast-foundation @microsoft/fast-element @microsoft/fast-react-wrapper

Configure create-react-app#

create-react-app ships with an eslint rule that makes working with FAST components difficult. There are two changes that will need to be made in the package.json:

Set the EXTEND_ESLINT environment variable in start, build, and test scripts

{    //...    "scripts": {        "start": "EXTEND_ESLINT=true react-scripts start",        "build": "EXTEND_ESLINT=true react-scripts build",        "test": "EXTEND_ESLINT=true react-scripts test",    }    // ...}

note

The above will not work on Windows. You can adjust the scripts to use cross-env to add Windows support.

Override the eslintConfig field to turn off the 'no-unused-expressions' rule

{    //..    "eslintConfig": {        "extends": "react-app",        "rules": {            "no-unused-expressions": "off"        }    },    //..}

See configuring eslint for more information.

Using the components#

With all the basic pieces in place, let's run our app in dev mode with npm start. Right now, it displays the React logo and some editing instructions, since we haven't added any code or interesting HTML. Let's change that.

First, open your src/app.js file and add the following code:

import {     provideFASTDesignSystem,     fastCard,     fastButton} from '@microsoft/fast-components';import { provideReactWrapper } from '@microsoft/fast-react-wrapper';import React from 'react';
const { wrap } = provideReactWrapper(    React,     provideFASTDesignSystem());
export const FastCard = wrap(fastCard());export const FastButton = wrap(fastButton())

This code uses the FAST Design System to register the <fast-card> and <fast-button> components while automatically wrapping them into React components. Once you save, the dev server will rebuild and refresh your browser. However, you still won't see anything. To get some UI showing up, we need to write some HTML that uses our components. Replace the App component in your src/app.js file with the following:

function App() {    return (      <FastCard>          <h2>FAST React</h2>          <FastButton appearance="accent" onClick={() => console.log("clicked")}>Click Me</FastButton>      </FastCard>    );}

To add a splash of style, add the following to the src/App.css:

fast-card {  padding: 16px;  display: flex;  flex-direction: column;}
h2 {  font-size: var(--type-ramp-plus-5-font-size);  line-height: var(--type-ramp-plus-5-line-height);}
fast-card > fast-button {  align-self: flex-end;}

Congratulations! You're now set up to use FAST and React!

Using the React Wrapper#

Above, we leveraged the @microsoft/fast-react-wrapper library to enable seamless integration of FAST Components. There are a few additional ways to use this API for different web component scenarios.

Wrapping Design System Components#

Previously, you've seen that we can wrap a Design System component by passing its registration function to the wrap method as follows:

const { wrap } = provideReactWrapper(    React,     provideFASTDesignSystem());
export const FastButton = wrap(fastButton())

This code creates a wrapper that is configured with a React-compatible API and a Design System instance. When passing a Design System as the second parameter, you can then pass component registration functions to the wrap helper. The helper will both register the web component with the Design System and wrap it in a type-safe React component, all with a single call.

Alternatively, you can skip providing the Design System to the wrapper, and use the generated registry to manually register all previously wrapped components.

const { wrap, registry } = provideReactWrapper(React);
export const FastButton = wrap(fastButton())
provideFASTDesignSystem()    .register(registry)

The final option is to handle everything by hand:

const { wrap } = provideReactWrapper(React);
export const FastButton = wrap(fastButton())
provideFASTDesignSystem()    .register(        fastButton()    );

Wrapping FAST Components#

The wrap helper can also wrap any FAST Web Component defined using the @customElement decorator or by manually calling FASTElement.define. To do so, pass the custom element class to the wrapper.

@customElement({  name: 'my-component',  template:...,  styles:...})class _MyComponent extends FASTElement {
}
export const MyComponent = provideReactWrapper(React).wrap(_MyComponent);

Wrapping VanillaJS Web Components#

If you have a component from a 3rd party library, not written with FAST, or a VanillaJS Web Component, you can wrap that as well. In this scenario you will have to provide some additional information, such as the element name and the list of properties that should be handled by the wrapper rather than React. Components created with libraries like Lit require the element name to be configured but not the properties, while some other libraries or hand-written components may also require the property list. This depends on how the component was defined. Below is an example of configuring both the name and the property list.

import { CoolComponent as _CoolComponent } from '@cool/component';
const { wrap } = provideReactWrapper(React);
export const CoolComponent = wrap(  _CoolComponent,  {    name: 'cool-component',    properties: [      'list',      'properties',      'here'    ]  });

Configuring Custom Events#

If the wrapped component uses custom events that you intend to use from React, you will need to manually configure a mapping from React event name to the native event name. Here's an example of what that would look like if you wanted to leverage the FAST MenuItem's expanded-change event:

const { wrap } = provideReactWrapper(    React,     provideFASTDesignSystem());
export const FastMenuItem = wrap(    fastMenuItem(),    {      events: {        onExpandedChange: 'expanded-change'      }    })

Additional Notes#

create-react-app#

FAST makes use of decorators to define components. At this time, create-react-app does not support decorators. This won't be a problem when using components imported from FAST because they have already been transpiled by TypeScript - but to create components in a create-react-app application you'll need to do one of the following:

Define components without decorators
Ejectcreate-react-app and change Babel to support decorators
Use an intermediary like react-app-rewired

Working without the fast-react-wrapper#

The @microsoft/fast-react-wrapper library described above addresses all the challenges involved in using Web Components from React. We strongly recommend using this library for integration. However, if you cannot use this library or want to explore other options, below you'll find information on alternative approaches.

HTML Attributes#

React is capable of rendering custom HTML elements and binding data to them, but it is beneficial to understand how React does this. React will apply all props to a custom HTML element as HTML attributes - including non-primitive types such as arrays and objects. Where some UI libraries provide binding syntaxes to distinguish setting properties, attributes, and events, React does not. This means that it can be very easy to end up with my-prop="[object Object]" in your HTML. React is exploring solutions in this issue. See the section on interop layers for a work-around for this issue.

Custom events#

React's synthetic eventing system comes with an unfortunate side-effect of being incapable of declaratively applying CustomEvent listeners. interop layers can be used to address this issue. Alternatively, a ref can be used on the custom element to imperatively apply the event listener to the HTML element directly.

Interop layers: @skatejs/val and reactify-wc#

@skatejs/val is a small library that wraps React's createElement function and provides the ability direct React props explicitly to HTML attributes, DOM properties, or to declarative event listeners.

Another good option is reactify-wc. It provides similar capabilities as @skatejs/val but does so by creating component wrappers.

TypeScript and TSX support#

If you're using TypeScript, you'll need to augment the JSX.IntrinsicElements interface to use custom elements in TSX. To do so, create a custom-elements.d.ts file in your source directory and add the following:

// custom-elements.d.tsdeclare namespace JSX {    interface IntrinsicElements {        /**         *  React.DetailedHTMLProps<React.HTMLAttributes<HTMLElement>, HTMLElement> allows setting standard HTML attributes on the element         */        "my-element": React.DetailedHTMLProps<React.HTMLAttributes<HTMLElement>, HTMLElement> & {            "my-attribute-name": string;        };    }}