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- You can handle a Promise in React using useEffect to call the Promise, and a useState to store the result. It’s also useful to set up some other values to track the state of the asynchronous action.
blog.stackademic.com/the-best-way-to-handle-promises-in-react-b229276a4076
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Promises are essentially a way of handling asynchronous operations, a common example of this is performing API requests in React. To work these into the React lifecycle, we can use the useState hook to store the result of the promise when it is resolved and re-render the component.
You can handle a Promise in React using useEffect to call the Promise, and a useState to store the result. It's also useful to set up some other values to track the state of the asynchronous action. We'll start off with our Promise.
Nov 7, 2023 · In React, Promises are commonly used for handling asynchronous operations like making API calls, managing state updates, and controlling the component lifecycle. Here’s a basic example of using...
Feb 6, 2024 · You can handle a Promise in React using useEffect to call the Promise, and a useState to store the result. It’s also useful to set up some other values to track the state of the asynchronous action.
- Overview
- Features
- Table of Contents
- Terminology
- API
- Caching
- Tags
- Refreshing resources
- 🌐 HTTP Resources
Simple and declarative use of Promises in your React components. Observe their state and refresh them in various advanced ways.
Now with built-in support for 🌐 HTTP!
•Simple and declarative use of Promises, loading- and error views
•Built-in support to load data with HTTP resources
•Auto-refresh after timeout or on window focus
•Type-Safe API
•No "double-loading" when using "same" Promise in different places in your app
•Caching with support for custom tags
(Async) resource
An async resource (or just resource) represents something that has to be loaded asynchronously. Asynchronous loading involves different states, like "loading" or "loading is done", that should be reflected in the UI. Basically async resources encapsulating Promises and equipping them with relevant features like observing the Promises state or caching the result.
Async loader (function)
The async loader function is simply a function returning a Promise and thus acts as the basic input for async resources.
usePromise
Get the result of a Promise by passing an async loader with the relevant loader parameters and an optional configuration to the usePromise hook.
getAsyncResource
This is an alternative and more advanced API to the usePromise hook. For details see Lazy Loading with Async Resources. The usePromise hook uses the getAsyncResource-API under the hood and is basically just a shortcut for getAsyncResource(asyncLoader, loaderParameters, options).use(). Get an async resource by passing an async loader with the relevant loader parameters and an optional configuration to the getAsyncResource function.
Async resource
The async resource returned by getAsyncResource has the following API.
Caching the result of async loader functions is essential to make this library work. Without it, components will end-up in an endless render-loop, since the re-render after finished loading will trigger the loader function again.
To break this loop, the result (and even the error) of the loader function is cached inside the resource instance. If a cached result exists, the loader must not be called again and the cached value is used instead.
You can assign tags to resources. A tag is simply a string that classifies the resource. In advanced scenarios you might want to assign multiple tags to one resource, expressing the resource matches different classifications.
Using relevant tags creates the possibility to be very expressive and flexible when it comes to accessing multiple resources at once, e.g. when you need to refresh them.
If a resource has a cached result, the async loader function must not be called again and the cached value is used instead. To invalidate the cached value you can call the refresh() method on the resource or use the global refresh() method. As a result the async loader function will automatically be called again and a component update is triggered when the result is available.
Refreshing resources that are not used in any mounted component, will suspend the reload until the resource is actually used the next time.
A major use case of this library might be to load data from some HTTP-API. This is exactly why a preconfigured HTTP resource is included in this package. The simplest way is to use the useHttpData() method to GET data from a given URL.
Important: As this feature requires the axios package you need to include it in your dependencies!
Promises provide a more convenient API to do things asynchronously. Before promises async things were done with callbacks so promises are an improvement on callbacks . Callback Example
May 4, 2020 · Using Promises in React with hooks or with classes isn't as easy as it might seem at first. Let's look at a simple example to illustrate the problem: const [result, setResult] = useState<string | undefined>(undefined) useEffect(() => { promiseReturningFunction(a).then(res => setResult(res)) }, [a]) This code might not do what you want it to do ...
