@leanjs/react

This package contains React bindings for @leanjs/core runtime. These React bindings provide idiomatic type-safe access to your LeanJS runtime.

Installation

yarn add @leanjs/react @leanjs/core

Usage

First, you must create your custom React bindings for your runtime.

// shared-runtime.ts

// 1. Configure your runtime

const defaultState = {
  locale: "en", // define your default state accordingly, this is just an example
};

// configureRuntime is a generic TypeScript function. You can pass a type to it
// if the types of your shared state don't match the inferred types from defaultState
export const { createRuntime } = configureRuntime(defaultState)({
  onError: () => {}, // add a proper logger here
});

// 2. Create bindings for your runtime

export const {
  useGetter,
  useSetter,
  useLoading,
  useError,
  useRuntime,
  HostProvider,
} = createRuntimeBindings(createRuntime);

// ⚠️ We recommend to split in two different packages the logic of
// configuring your runtime and creating its React bindings.
// For sake of simplicity it's in one file shared-runtime.ts in this example.

Add a HostProvider at the root of your component tree, e.g.

// It's recommended to move your ./shared-runtime file to its own package
import { createRuntime, HostProvider } from "./shared-runtime";

const runtime = createRuntime();
const origin = process.env.LEAN_ORIGIN; // e.g. http://localhost:55555

export function App({ children }) {
  return (
    <HostProvider origin={origin} runtime={runtime}>
      {children}
    </HostProvider>
  );
}

Use any of our hooks in your components, e.g.

// It's recommended to move your ./shared-runtime file to its own package
import { useGetter } from "./shared-runtime";

export function LocaleComponent() {
  const locale = useGetter("locale");

  return <p>Current locale is {locale}</p>;
}

API

To use any of the following, you must first call createRuntimeBindings. Read the usage section above for more info.

useGetter

Hook to get the current state of a given state property.

Arguments:

1. State property, required.
2. Loader function, optional.

The output is the current state of the given property.

Example:

// where does shared-runtime come from? Read the "Usage" section at the top
import { useGetter } from "./shared-runtime";

export function LocaleComponent() {
  const locale = useGetter("locale", () =>
    fetch("/api/settings")
      .then((response) => response.json())
      .then((data) => data.locale)
  );

  return <p>Locale is {locale}</p>;
}

useLoading

Hook to get the loading state of a given state property.

Arguments:

1. State property, required.

The output is a boolean indicating if the given state property is loading.

Example:

// where does shared-runtime come from? Read the "Usage" section at the top
import { useLoading } from "./shared-runtime";

export function LocaleSpinner() {
  const loading = useLoading("locale");

  if (loading) {
    return <p>Loading...</p>;
  } else {
    return null;
  }
}

useError

Hook to get the error state if a given state property failed to load.

Arguments:

1. State property, required.

The output is undefined or a string with the error message.

Example:

// where does shared-runtime come from? Read the "Usage" section at the top
import { useError } from "./shared-runtime";

export function LocaleErrorMessage() {
  const error = useError("locale");

  if (error) {
    return <p>Oops, locale error: {error} </p>;
  } else {
    return null;
  }
}

useSetter

Hook to update the value of a given state property.

Arguments:

1. State property, required.

The output is a function to update the value of the given state property.

Example:

// where does shared-runtime come from? Read the "Usage" section at the top
import { useSetter } from "./shared-runtime";

export function ThemeSelector() {
  const shareTheme = useSetter("theme");

  return (
    <>
      <label for="theme-select">Choose a theme:</label>
      <select
        onChange={(e) => shareTheme(e.target.value)}
        name="theme"
        id="theme-select"
      >
        <option value="">--Please choose an option--</option>
        <option value="dark">Dark</option>
        <option value="light">Light</option>
      </select>
    </>
  );
}

HostProvider

It sets in the React context values that are shared across micro-apps in the same component tree. Props:

• runtime: Runtime, required. Your LeanJS runtime.
• origin: string, required. Origin where your micro-frontends are. For development, use the address where you run your Lean centralized dev server, e.g. http://localhost:55555. Use the address of your CDN in production, e.g. https://cdn.my-product.com.
• errorComponent, optional.
• fallback, optional.

Example:

// where does shared-runtime come from? Read the "Usage" section at the top
import { createRuntime, HostProvider } from "./shared-runtime";

const runtime = createRuntime();
const origin = process.env.LEAN_ORIGIN; // e.g. http://localhost:55555

export function App({ children }) {
  return (
    <HostProvider origin={LEAN_ORIGIN} runtime={runtime}>
      {children}
    </HostProvider>
  );
}

useRuntime

It returns the shared runtime from the context.

Example:

// where does shared-runtime come from? Read the "Usage" section at the top
import { useRuntime } from "./shared-runtime";

// HostProvider must be an ancestor of the following component
export function Component() {
  const runtime = useRuntime(); // do something with runtime

  return <h1>My component</h1>;
}