Shubham Ankit

Shubham Ankit

1549809803

React Hooks, Suspense, and Memo

Things are blowing up in the React community lately! Between the suspensewe had for a few months, Create React App v2, Hooks, Memo -- React developers new and old have their plates full with new toys to play with. I finally got some time to dig into the new React.memo(), React.lazy() and <Suspense /> APIs, as well as the proposed Hooks API.

PureComponent for Functional Components

A new technique to memoize! React.memo() is a HOC that prevents a component from rendering on props change if the props are the same. It basically runs a shallow equal on the props in the shouldComponentUpdate()lifecycle, but for functional components that don’t have access to it (without switching to a class).

const MyComponent = React.memo(function MyComponent(props) {
  /* render using props */
});

And if the props contain complex objects, we can add a function inside the component to check:

function MyComponent(props) {
  /* render using props */
}
function areEqual(prevProps, nextProps) {
  /*
  return true if passing nextProps to render would return
  the same result as passing prevProps to render,
  otherwise return false
  */
}
export default React.memo(MyComponent, areEqual);

This is a great performance gain for component and design systems that rely on functional components for rendering lower-level UI elements.

A callback “cache”

There’s also a new hook implemented that uses the same memoization logic on functions. It prevents the function from being called again unless it’s parameters (or variables you specify) change:

const memoizedValue = useMemo(() => computeExpensiveValue(a, b), [a, b]);

The suspense is over 🌟

The first thing I wanted to dig into was Suspense, since it's actually implemented (if not incomplete). After watching Dan's incredible talk about Suspense at ReactFest 2018 in March, I was excited that React was making lazy loading a priority enough to incoporate it into their API. Rather than relying on a library like react-loadable or configurations in Webpack, I can just simply:

const OtherComponent = React.lazy(() => import('./OtherComponent'));

function MyComponent() {
return (
<div>
<Suspense fallback={<div>Loading…</div>}>
<OtherComponent />
</Suspense>
</div>
);
}

Not only do I get the benefit of deferring the loading of my components bundle (making the app load initially faster), but I can also plug in any loading component. It makes illusions like skeleton screens an effortless task.

You can see a live example on CodeSandbox:

Hooks

Recently React has proposed a new, more functional way of handling state using “hooks”, rather than relying on the lifecycle methods of a React component. You can find the entire proposal in the React docs here.

Using them is simple, and offers a lower LOC with functional components compared to the class alternative.

function YourComponent({ text }) {
const [ theText, updateText] = useState(text)
const changeText = ({ target: { value } }) => {
updateText(value)
}
return(
<button onClick={() => changeText}>
{theText}
</button>
)
}

To handle any side effects in the component, throw in a useEffect() inside the functional component to run code on each state change / re-render.

One of the best part of hooks is their functional nature (FP FTW). You can extract the hook and effect into a separate function, and re-use that hook across multiple components in the app.

Hooks = Less Compiled Code

One of the best parts of the addition of hooks is the ability to abandon classes for stateful logic in favor of more efficient functions. If you’ve ever looked at most compiled JS code, because of the way classes work (being syntactic sugar over prototypes), using a class in your app bloats your code immensely with polyfills.

This class:

class Test extends React {
constructor() {
super()
this.state = {}
}
render() {
return <div>Test</div>
}
}

compiles to:

“use strict”;

var _createClass = function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if (“value” in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; }();

function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError(“Cannot call a class as a function”); } }

function _possibleConstructorReturn(self, call) { if (!self) { throw new ReferenceError(“this hasn’t been initialised - super() hasn’t been called”); } return call && (typeof call === “object” || typeof call === “function”) ? call : self; }

function _inherits(subClass, superClass) { if (typeof superClass !== “function” && superClass !== null) { throw new TypeError("Super expression must either be null or a function, not " + typeof superClass); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, enumerable: false, writable: true, configurable: true } }); if (superClass) Object.setPrototypeOf ? Object.setPrototypeOf(subClass, superClass) : subClass.proto = superClass; }

var Test = function (_React) {
_inherits(Test, _React);

function Test() {
_classCallCheck(this, Test);

var _this = _possibleConstructorReturn(this, (Test.__proto__ || Object.getPrototypeOf(Test)).call(this));

_this.state = {};
return _this;

}

_createClass(Test, [{
key: “render”,
value: function render() {
return React.createElement(
“div”,
null,
“Test”
);
}
}]);

return Test;
}(React);

In contrast, if you use a function (unless it’s a ES6 arrow function), it compiles just as it appears – since functions are so broadly supported (being so primitive/early JS API). Even when you take array destructuring into account, the code is still less than the class, while being able to use state:

function Test(props) {
const [counter, increment] = useState(0);
return <h1>Hello</h1>;
}
“use strict”;

var _slicedToArray = function () { function sliceIterator(arr, i) { var _arr = []; var _n = true; var _d = false; var _e = undefined; try { for (var _i = arrSymbol.iterator, _s; !(_n = (_s = _i.next()).done); _n = true) { _arr.push(_s.value); if (i && _arr.length === i) break; } } catch (err) { _d = true; _e = err; } finally { try { if (!_n && _i[“return”]) _i"return"; } finally { if (_d) throw _e; } } return _arr; } return function (arr, i) { if (Array.isArray(arr)) { return arr; } else if (Symbol.iterator in Object(arr)) { return sliceIterator(arr, i); } else { throw new TypeError(“Invalid attempt to destructure non-iterable instance”); } }; }();

function Test(props) {
var _useState = useState(0),
_useState2 = _slicedToArray(_useState, 2),
counter = _useState2[0],
increment = _useState2[1];

return React.createElement(
“h1”,
null,
“Hello”
);
}

A more composable future for React

It’s been nice to see the improvements to the React API over the past year. The team does a fantastic job of maintaining legacy API and not breaking apps (Facebook still using React.createElement), and the addition of new features all address key issues developers have. I can’t tell you how many times I’ve had to take a functional component and convert it into a class just for a single stateful boolean, where now I’ll be able to just drop a hook in the top of the function (and memoize it to get the same perf as PureComponent!).


By : Ryosuke


#reactjs #javascript

What is GEEK

Buddha Community

John Cozen

1550433155

Very helpful, concise writeup.Thanks!

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

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

Juana  O'Keefe

Juana O'Keefe

1603127640

Hooks, Hooks, Hooks!

Prior to 2018, React, an already powerful and widely-used javascript library for building user interfaces, had 3 cumbersome issues:

  1. Reusing logic: in order to to create dynamic interfaces where state is manipulated, logic was constantly being copied for seemingly simple tasks like updating the state from a form field. This often would lead to complicated and bloated data structures.
  2. Giant components: logic often times gets split amongst various lifecycle. methods in order to keep your application working.
  3. Confusing classes: invariably with reused logic and oversized components, our classes themselves can become confusing for both user and the machine.

As Dan Abramov of the React Dev team describes it, these are really three separate issues, but rather systems of the same problem: before 2018, _React did not provide a stateful primitive that is simpler than incorporating a class component and its associated logic. _At one point, React used mixins to pseudo-resolve this issue, but that ultimately created more problems that it solved.

How did the React team resolve this seemingly singular, but hugely impactful inconvenience? Hooks to the rescue.

Image for post

#software-engineering #react-conf-2018 #hooks #react #react-conference #react native