Understanding how React Suspense works
Tags: react, abotwrotethis
Published: 2023-04-13 06:12:03

React Suspense is a powerful feature that can help you manage the asynchronous data loading in your React applications. It allows you to create a smooth user experience by suspending the rendering of components until the required data is available. In this blog post, we will dive deep into React Suspense and explore how it works.

## What is React Suspense?

React Suspense is a feature introduced in React 16.6 as an experimental feature. It is designed to manage asynchronous data loading and improve the user experience by avoiding UI freezes or delays. React Suspense allows you to suspend rendering of a component tree until the required data is available, providing your users with a seamless experience.

## How Does React Suspense Work?

React Suspense works by making use of two new APIs: `Suspense` and `lazy`.

### The Suspense Component

The `Suspense` component is a new component in React that allows you to suspend the rendering of a component tree until all of its subcomponents have loaded. It achieves this using its `fallback` prop, which is a component that is rendered while the suspended component is loading.

```js
<Suspense fallback={<Spinner />}>
  <ComponentThatLoadsData />
</Suspense>
```

In this example, the `ComponentThatLoadsData` will be suspended and not rendered until the required data is available. In the meantime, the `Spinner` component will be rendered instead.

### The Lazy API

The `lazy` API is a function that allows you to lazy load a component. Lazy loading means that the component will only be loaded when it is actually required, which can help to improve the initial load time of your application. Lazy loading is especially useful for large components that are not used frequently.

```js
const ComponentThatLoadsData = lazy(() => import('./ComponentThatLoadsData'))
```

In this example, the `ComponentThatLoadsData` will only be loaded when it is actually required. This can be useful for improving the performance of your application, as it reduces the amount of code that needs to be loaded upfront.

## What are Data Fetching Libraries?

Data fetching libraries are libraries that allow you to fetch data from an API or other external data source. There are many data fetching libraries available, including `axios`, `fetch`, and `GraphQL`. These libraries can be integrated with React Suspense to manage asynchronous data loading.

### Axios

Axios is a popular data fetching library that allows you to make HTTP requests from your application. It is based on the XMLHttpRequest API and supports CORS. Axios can be integrated with React Suspense using a custom `useAxios` hook.

```js
import { useAxios } from 'use-axios';

function ComponentThatLoadsData() {
  const { data, error } = useAxios('/api/data');

  if (error) {
    throw new Error('Failed to load data');
  }

  return <div>{data}</div>;
}
```

In this example, the `useAxios` hook is used to fetch the data from the `/api/data` endpoint. If an error occurs during the data fetch, an error message is thrown. Otherwise, the data is rendered in the component.

### Fetch

Fetch is a newer data fetching API that is built into most modern browsers. It is a lightweight API that allows you to make HTTP requests from your application. Like Axios, it can be integrated with React Suspense using a custom `useFetch` hook.

```js
import { useFetch } from 'use-fetch';

function ComponentThatLoadsData() {
  const { data, error } = useFetch('/api/data');

  if (error) {
    throw new Error('Failed to load data');
  }

  return <div>{data}</div>;
}
```

In this example, the `useFetch` hook is used to fetch the data from the `/api/data` endpoint. If an error occurs during the data fetch, an error message is thrown. Otherwise, the data is rendered in the component.

### GraphQL

GraphQL is a query language for APIs that allows you to retrieve only the data you need. It is often used in combination with React to build highly performant applications. GraphQL can be integrated with React Suspense using a custom `useQuery` hook.

```js
import { useQuery } from '@apollo/client';

function ComponentThatLoadsData() {
  const { data, loading, error } = useQuery(GET_DATA);

  if (loading) {
    return <Spinner />;
  }

  if (error) {
    throw new Error('Failed to load data');
  }

  return <div>{data}</div>;
}
```

In this example, the `useQuery` hook is used to fetch the data using the `GET_DATA` query. If the data is still loading, a `Spinner` component is rendered. If an error occurs during the data fetch, an error message is thrown. Otherwise, the data is rendered in the component.

## Conclusion

React Suspense is a powerful feature that allows you to manage asynchronous data loading in your React applications. By suspending the rendering of a component tree until the required data is available, you can provide a seamless user experience. With the help of data fetching libraries like Axios, Fetch, and GraphQL, you can build applications that load data efficiently and performantly.