Dylan North

Dylan North

1565774421

Create a Custom useFetch() React Hook

Originally published by Chris Nwamba at scotch.io

Table of Contents

  • Abstracting fetch into useFetch()
  • Avoiding reference loops
  • useEffect’s return error
  • Handling errors
  • Setting loading indicators
  • Usage
  • Final thoughts
  1. the function name to start with use and
  2. the function may call other Hooks

The whole idea behind custom hooks is just so that we can extract component logic into reusable functions.

Often times as we build out React applications, we see ourselves writing almost the same exact codes in two or more different components. Ideally what we could do in such cases would be to extract that recurrent logic into a reusable piece of code (hook) and reuse it where the need be.

Before hooks, we share stateful logic between components using render props and higher order components, however, since the introduction of hooks and since we came to understand how neat they make these concepts, it no longer made sense to keep using those. Basically, when we want to share logic between two JavaScript functions, we extract it to a third function possibly because both components and hooks are equally just functions.

Abstracting fetch into useFetch()

The rationale behind this move is not different from what we have already explained above. Compared to using the native fetch API out of the box, abstracting it into the useFetch hook gives us a one-liner ability, more declarative code style, reusable logic and an overall cleaner code as we’ll see in a minute. Consider this simple useFetch example:

const useFetch = (url, options) => {
  const [response, setResponse] = React.useState(null);
  useEffect(async () => {
      const res = await fetch(url, options);
      const json = await res.json();
      setResponse(json);
  });
  return response;
};

Here, the effect hook called useEffect is used to perform to major functions —

  1. fetch the data with the native fetch API and
  2. Set the data in the local state of the component with the state hook’s update function.

Also notice that the promise resolving happens with async/await.

Avoiding reference loops

The effect hook runs on two occasions — When the component mounts and also when the component updates. What this means is, if nothing is done about the useFetch example above, we will most definitely run into a scary recurrent loop cycle. Why? Because we are setting the state after every data fetch, as a result, when we set the state, the component updates and the effect runs again.

Obviously, this will result in an infinite data fetching loop and we don’t want that. What we do want, is to only fetch data when the component mounts and we have a neat way of doing it. All we have to do is provide an empty array as second argument to the effect hook, this will stop it from activating on component updates but only when the component is mounted.

 useEffect(async () => {
      const res = await fetch(url, options);
      const json = await res.json();
      setResponse(json);
  }, []); // empty array

The second is an array containing all the variables on which the hook depends on. If any of the variables change, the hook runs again, but if the argument is an empty array, the hook doesn’t run when updating the component since there are no variables to watch.

UseEffect’s return error

You may have noticed that in the effect hook above, we are using async/await to fetch data. However, according to documentation stipulations, every function annotated with async returns an implicit promise. So in our effect hook, we are returning an implicit promise whereas an effect hook should only return either nothing or a clean up function.

So by design, we are already breaking this rule because —

  1. We are not returning nothing
  2. A promise does not clean up anything

As a result, if we go ahead with the code as is, we will get a warning in the console pointing out the fact that useEffect function must return a cleanup function or nothing.

Simply put, using async functions directly in the useEffect() function is frowned at. What we can do to fix this is exactly what is recommended in the warning above. Write the async function and use it inside the effect.

React.useEffect(() => {
    const fetchData = async () => {
      const res = await fetch(url, options);
      const json = await res.json();
      setResponse(json);
    };
    fetchData();
  }, []);

Instead of using the async function directly inside the effect function, we created a new async function fetchData() to perform the fetching operation and simply call the function inside useEffect. This way, we abide by the rule of returning nothing or just a cleanup function in an effect hook. And if you should check back on the console, you won’t see any more warnings.

Handling errors

One thing we haven’t mentioned or covered so far is how we can handle error boundaries in this concept. Well, it’s not complicated, when using async/await, it is common practice to use the good old try/catch construct for error handling and thankfully it will also work for us here.

const useFetch = (url, options) => {
  const [response, setResponse] = React.useState(null);
  const [error, setError] = React.useState(null);
  React.useEffect(() => {
    const fetchData = async () => {
      try {
        const res = await fetch(url, options);
        const json = await res.json();
        setResponse(json);
      } catch (error) {
        setError(error);
      }
    };
    fetchData();
  }, []);
  return { response, error };
};

Here, we used the very popular JavaScript try/catch syntax to set and handle error boundaries. The error itself is just another state initialized with a state hook so whenever the hook runs, the error state resets. However, whenever there is an error state, the component renders feedback to the user or practically you can perform any desired operation with it.

Setting loading indicators

You may already know this, but i still feel that it’ll be helpful to point out that you can use hooks to handle loading states for your fetching operations. The good thing is, It’s just another state variable managed by a state hook so if we wanted to implement a loading state in our last example, we’ll set the state variable and update our useFetch() function accordingly.

const useFetch = (url, options) => {
  const [response, setResponse] = React.useState(null);
  const [error, setError] = React.useState(null);
  const [isLoading, setIsLoading] = React.useState(false);
  React.useEffect(() => {
    const fetchData = async () => {
      setIsLoading(true);
      try {
        const res = await fetch(url, options);
        const json = await res.json();
        setResponse(json);
        setIsLoading(false)
      } catch (error) {
        setError(error);
      }
    };
    fetchData();
  }, []);
  return { response, error, isLoading };
    };

Usage

We cannot complete this tutorial without working on a hands-on demonstration to put everything we’ve talked about in practice. Let’s build a mini app that will fetch a bunch of dog images and their names. We’ll use useFetch to call the very good dog API for the data we’ll need for this app.

First we define our useFetch() function which is exactly the same as what we did before. We will simply reuse the one we created while demonstrating error handling above to explain the data fetching concept in practice since it already has most of the things we’ll need.

const useFetch = (url, options) => {
  const [response, setResponse] = React.useState(null);
  const [error, setError] = React.useState(null);
  React.useEffect(() => {
    const fetchData = async () => {
      try {
        const res = await fetch(url, options);
        const json = await res.json();
        setResponse(json);
      } catch (error) {
        setError(error);
      }
    };
    fetchData();
  }, []);
  return { response, error };
};

Next, we create the App() function that will actually use our useFetch() function to request for the dog data that we need and display it on screen.

function App() {
  const res = useFetch("https://dog.ceo/api/breeds/image/random", {});
  if (!res.response) {
    return <div>Loading...</div>
  }
  const dogName = res.response.status
  const imageUrl = res.response.message
  return (
    <div className="App">
      <div>
        <h3>{dogName}</h3>
        <div>
          <img src={imageUrl} alt="avatar" />
        </div>
      </div>
    </div>
  );
}

Here, we just passed the url into the useFetch() function with an empty options object to fetch the data for the cat. It’s really that simple, nothing elaborate or complex. Once we’ve fetched the data, we just extract it from the response object and display it on screen. Here’s a demo on Codesandbox:


Final thoughts

Data fetching has always been an issue to contend with when building frontend-end applications, this is usually because of all the edge cases that you will need to account for. In this post, we have explained and made a small demo to explain how we can declaratively fetch data and render it on screen by using the useFetch hook with the native fetch() API.

Originally published by Chris Nwamba at scotch.io

=======================================================

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#reactjs #javascript #web-development

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Create a Custom useFetch() React Hook
Autumn  Blick

Autumn Blick

1598839687

How native is React Native? | React Native vs Native App Development

If you are undertaking a mobile app development for your start-up or enterprise, you are likely wondering whether to use React Native. As a popular development framework, React Native helps you to develop near-native mobile apps. However, you are probably also wondering how close you can get to a native app by using React Native. How native is React Native?

In the article, we discuss the similarities between native mobile development and development using React Native. We also touch upon where they differ and how to bridge the gaps. Read on.

A brief introduction to React Native

Let’s briefly set the context first. We will briefly touch upon what React Native is and how it differs from earlier hybrid frameworks.

React Native is a popular JavaScript framework that Facebook has created. You can use this open-source framework to code natively rendering Android and iOS mobile apps. You can use it to develop web apps too.

Facebook has developed React Native based on React, its JavaScript library. The first release of React Native came in March 2015. At the time of writing this article, the latest stable release of React Native is 0.62.0, and it was released in March 2020.

Although relatively new, React Native has acquired a high degree of popularity. The “Stack Overflow Developer Survey 2019” report identifies it as the 8th most loved framework. Facebook, Walmart, and Bloomberg are some of the top companies that use React Native.

The popularity of React Native comes from its advantages. Some of its advantages are as follows:

  • Performance: It delivers optimal performance.
  • Cross-platform development: You can develop both Android and iOS apps with it. The reuse of code expedites development and reduces costs.
  • UI design: React Native enables you to design simple and responsive UI for your mobile app.
  • 3rd party plugins: This framework supports 3rd party plugins.
  • Developer community: A vibrant community of developers support React Native.

Why React Native is fundamentally different from earlier hybrid frameworks

Are you wondering whether React Native is just another of those hybrid frameworks like Ionic or Cordova? It’s not! React Native is fundamentally different from these earlier hybrid frameworks.

React Native is very close to native. Consider the following aspects as described on the React Native website:

  • Access to many native platforms features: The primitives of React Native render to native platform UI. This means that your React Native app will use many native platform APIs as native apps would do.
  • Near-native user experience: React Native provides several native components, and these are platform agnostic.
  • The ease of accessing native APIs: React Native uses a declarative UI paradigm. This enables React Native to interact easily with native platform APIs since React Native wraps existing native code.

Due to these factors, React Native offers many more advantages compared to those earlier hybrid frameworks. We now review them.

#android app #frontend #ios app #mobile app development #benefits of react native #is react native good for mobile app development #native vs #pros and cons of react native #react mobile development #react native development #react native experience #react native framework #react native ios vs android #react native pros and cons #react native vs android #react native vs native #react native vs native performance #react vs native #why react native #why use react native

What are hooks in React JS? - INFO AT ONE

In this article, you will learn what are hooks in React JS? and when to use react hooks? React JS is developed by Facebook in the year 2013. There are many students and the new developers who have confusion between react and hooks in react. Well, it is not different, react is a programming language and hooks is a function which is used in react programming language.
Read More:- https://infoatone.com/what-are-hooks-in-react-js/

#react #hooks in react #react hooks example #react js projects for beginners #what are hooks in react js? #when to use react hooks

How to Fix Memory Leaks with a Simple React Custom Hook

See error logs in your console with the message “Cannot perform state update on an unmounted component” from your React application? There is a simple cause and easy fix.

The Cause

React components which run asynchronous operations and perform state updates can cause memory leaks if state updates are made after the component is unmounted. Here is a common scenario where this could pop up:

  1. User performs an action triggering an event handler to fetch data from an API.
  2. The user clicks on a link, navigating them to a different page, before (1) completes.
  3. The event handler from (1) completes the fetch, and calls a state setter function, passing it the data that was retrieved from the API.

Since the component was unmounted, a state setter function is being called in a component that is no longer mounted. Essentially, the setter function is updating state no longer exists. Memory Leak.

Here is a contrived example of unsafe code:

const [value, setValue] = useState({});
useEffect(() => {
    const runAsyncOperation = () => {
        setTimeout(() => {
            // MEMORY LEAK HERE, COMPONENT UNMOUNTED
            setValue({ key: 'value' });
        }, 1000);
    }
    runAsyncOperation();
    // USER NAVIGATES AWAY FROM PAGE HERE,
    // IN LESS THAN 1000 MS
}, []); 

#web-development #react #javascript #react-hook #custom-react-hook

Hayden Slater

1599277908

Validating React Forms With React-Hook-Form

Validating inputs is very often required. For example, when you want to make sure two passwords inputs are the same, an email input should in fact be an email or that the input is not too long. This is can be easily done using React Hook From. In this article, I will show you how.

Required Fields

The most simple, yet very common, validation is to make sure that an input component contains input from the user. React Hook Form basic concept is to register input tags to the form by passing register() to the tag’s ref attribute. As we can see here:

#react-native #react #react-hook-form #react-hook

The Ugly Side of React Hooks

In this post, I will share my own point of view about React Hooks, and as the title of this post implies, I am not a big fan.

Let’s break down the motivation for ditching classes in favor of hooks, as described in the official React’s docs.

Motivation #1: Classes are confusing

we’ve found that classes can be a large barrier to learning React. You have to understand how "this"_ works in JavaScript, which is very different from how it works in most languages. You have to remember to bind the event handlers. Without unstable syntax proposals, the code is very verbose […] The distinction between function and class components in React and when to use each one leads to disagreements even between experienced React developers._

Ok, I can agree that

thiscould be a bit confusing when you are just starting your way in Javascript, but arrow functions solve the confusion, and calling a_stage 3_feature that is already being supported out of the box by Typescript, an “unstable syntax proposal”, is just pure demagoguery. React team is referring to theclass fieldsyntax, a syntax that is already being vastly used and will probably soon be officially supported

class Foo extends React.Component {
  onPress = () => {
    console.log(this.props.someProp);
  }

  render() {
    return <Button onPress={this.onPress} />
  }
}

As you can see, by using a class field arrow function, you don’t need to bind anything in the constructor, and

this will always point to the correct context.

And if classes are confusing, what can we say about the new hooked functions? A hooked function is not a regular function, because it has state, it has a weird looking

this(aka_useRef_), and it can have multiple instances. But it is definitely not a class, it is something in between, and from now on I will refer to it as aFunclass. So, are those Funclasses going to be easier for human and machines? I am not sure about machines, but I really don’t think that Funclasses are conceptually easier to understand than classes. Classes are a well known and thought out concept, and every developer is familiar with the concept ofthis, even if in javascript it’s a bit different. Funclasses on the other hand, are a new concept, and a pretty weird one. They feel much more magical, and they rely too much on conventions instead of a strict syntax. You have to follow somestrict and weird rules, you need to be careful of where you put your code, and there are many pitfalls. Telling me to avoid putting a hook inside anifstatement, because the internal mechanism of hooks is based on call order, is just insane! I would expect something like this from a half baked POC library, not from a well known library like React. Be also prepared for some awful naming like useRef (a fancy name forthis),useEffect ,useMemo,useImperativeHandle(say whatt??) and more.

The syntax of classes was specifically invented in order to deal with the concept of multiple instances and the concept of an instance scope (the exact purpose of

this ). Funclasses are just a weird way of achieving the same goal, using the wrong puzzle pieces. Many people are confusing Funclasses with functional programming, but Funclasses are actually just classes in disguise. A class is a concept, not a syntax.

Oh, and about the last note:

The distinction between function and class components in React and when to use each one leads to disagreements even between experienced React developers

Until now, the distinction was pretty clear- if you needed a state or lifecycle methods, you used a class, otherwise it doesn’t really matter if you used a function or class. Personally, I liked the idea that when I stumbled upon a function component, I could immediately know that this is a “dumb component” without a state. Sadly, with the introduction of Funclasses, this is not the situation anymore.

#react #react-hooks #javascript #reactjs #react-native #react-hook #rethinking-programming #hackernoon-top-story