React is a JavaScript library that allows you to develop front-end code in minutes. It has pre-built methods and functions to perform certain tasks. React as a library includes complex terms like reconciliation, state, props, etc. What do they actually mean?
In this article, you will learn about this exaggerated concept more simply.
Components are small bit of reusable code that return a React element to be rendered on a webpage. It is a group of code that make up a single part of the webpage like buttons, navbar, cards, etc. It is just like a JavaScript function but returns a rendered element. It accepts parameters called "Props". Components are named with capital case.
Example Of Functional Component
function Heading(props) {
return <h1>Join us, {props.name}!</h1>;
}
Note:
JSX is JavaScript XML, which allows us to write HTML in React. It introduces XML-like tags and attributes to create React elements. It makes it easy to create React Components by letting you write HTML-like code in .jsx files. Instead of using complicated JavaScript, JSX makes the code readable and clean. React DOM uses camelCase for attribute naming such as htmlFor, onClick.
Example of JSX
<h1 className="head">This is H1!</h1>
Fragments in React allows you to return multiple elements from a component. It groups the list of elements without creating a extra DOM nodes. It cleans all the extra divs from the DOM. This quickly renders the UI.
Example of Fragments
const App = () => {
return (
<>
<h1>Eat</h1>
<button>Learn more</button>
<p>Code is Fun</p>
<button>Repeat</button>
</>
);
}
Note:
"Props" is a special keyword in React that stands for properties. It is used to transfer data between components. The follow of data transfer is uni-directional i.e from parent component to child component.
Example of Props
function Head(props) {
return <p>{props.children}</p>;
}
Note: Props is read-only, which ensures that child components don't manipulate the value coming from parent component.
Components need to keep track of certain values when user interacts. Let's say the light/dark mode theme toggle button changes its value(from light to dark & vice versa) when a user clicks on the button. Components need to remember the current value of theme. In React, this kind of component-specific memory is called state.
State is defined using a useState() hook; more on that later.
Example of defining state
const [index, setIndex] = useState(0)
Note: It's always a good practice to define state in a top-level component to share it easily with other child components and ensure a single source of truth.
Lifecycle methods are special functions you can use within React classes to perform actions at various stages of a component's existence. These stages are:
Purity in functional programming is when a given same input returns the same output. The inputs is the only factor that determine the output then the function is said to be pure.
In React a component is said to be pure when it returns the same output for the same input (viz props)
Strict Mode is a developmental feature in react that enables extra safety features to improve code quality. It shows warnings regarding potential errors and bugs into the code. It logs warning into the browser's console.
Example of Strict Mode
import { StrictMode } from 'react';
function App() {
return (
<>
<StrictMode>
<Header />
<Sidebar />
<Content />
<Footer />
</StrictMode>
</>
)
}
Hooks in React allows to use state and other React features without writing class components. Hooks are functions that provide access to React's state management, side effects, and other features.
Some commonly used hooks: useState, useMemo, useRef, etc.
Example of Hooks
import React, { useState } from "react"; // Importing useState hook;
function FavoriteColor() {
const [color, setColor] = useState("red"); // Initializing the state and setter function;
return (
<>
<h1>My favorite color is {color}!</h1>
<button
type="button"
onClick={() => setColor("blue")} // Updating the state;
>Blue</button>
<button
type="button"
onClick={() => setColor("red")} // Updating the state;
>Red</button>
<button
type="button"
onClick={() => setColor("yellow")} // Updating the state;
>Yellow</button>
</>
);
}
Note:
The Context API is used to share data like state, functions across the component tree without passing props down manually at every level. It avoids prop drilling by simplifying state management and sharing data across the component. With Context API the data is shared directly with the child component who will consume it.
The useContext() method is used to create a context. This function returns a context object with two components – a Provider and a Consumer.
The Provider is used to wrap the part of your component tree where you want the context to be available. It accepts a compulsory value prop that holds the data you want to share across other components.
The useContext hook is used to access the data.
Example of Context API
Create a context using createContext() method. Wrap child components in the Context Provider and supply the state value.
import { useState, createContext} from "react";
const UserContext = createContext();
function ParentCounter() {
const [count, setCount] = useState(10);
return (
<UserContext.Provider value={count}>
<h1>{`Current Count: ${count}!`}</h1>
<Button />
</UserContext.Provider>
);
}
Use useContext hook to access the value of age.
import { useContext } from "react";
function GrandChildConsumer() {
const age = useContext(UserContext);
return (
<>
<h1>This is GrandChildConsumer</h1>
<h2>{`Current Count: ${count}`}</h2>
</>
);
}
A Key is a special kind of attribute for list items in React. It acts as a unique identifier for each items when it is updated, deleted, or added.
Assigning index of the item as the Key is discouraged because if the items are rearranged it will affect the expected behavior.
Imagine in shopping cart you have 10 items added and each item have a unique index as a Key. Now, you decide to remove the first and fifth item from the cart. When the items are removed the indexing will change; the second item will become first and sixth item will become fifth item.
Example of Lists and Keys
const fruits = ["apple", "banana", "orange"];
function FruitList() {
return (
<ul>
{fruits.map((fruit, index) => (
<li key={index}> {fruit} </li>
))}
</ul>
);
}
React forms allows to collect and manage user input better than traditional HTML form. These forms are built using components and store the user inputs into state. There are two types of components:
In Controlled components, the form's state is managed by the component himself. This is the recommended approach for managing form data in React. When the user interacts with the form (e.g., typing in an input field), the component's state is updated to reflect the changes.
Example of Controlled Component
function ControlledInput() {
const [name, setName] = useState('');
const handleChange = (e) => {
setName(e.target.value);
}
return (
<div>
<label htmlFor="name">Name: </label>
<input type="text" id="name" value={name} onChange={handleChange} />
<p>Your name is: {name}</p>
</div>
);
}
Uncontrolled components rely on the DOM to manage the form data. The component doesn't directly control the form's state, but it can access the values using DOM methods like ref.
Example of Uncontrolled Component
function UncontrolledInput() {
const nameRef = useRef(null);
const handleClick = () => {
console.log(nameRef.current.value);
}
return (
<div>
<label htmlFor="name">Name: </label>
<input type="text" id="name" ref={nameRef} />
<button onClick={handleClick}>Get Name</button>
</div>
);
}
Note:
React Router is a standard library for routing in React. It enables navigation among various components in the React app. It allows changing the browser URL and syncing the UI with the URL. React Router is important for creating single-page applications (SPA) with navigation features.
First, you need to install React Router from your terminal.
Installing React Router
# If you are using npm npm install react-router-dom # If you are using yarn yarn add react-router-dom
Example of React Router
import { BrowserRouter, Routes, Route } from "react-router-dom";
import Home from "./pages/Home";
import About from "./pages/About";
import Contact from "./pages/Contact";
import NoPage from "./pages/NoPage";
export default function App() {
return (
<BrowserRouter>
<Routes>
<Route path="/" element={<Home />} />
<Route path="about" element={<About />} />
<Route path="contact" element={<Contact />} />
<Route path="*" element={<NoPage />} />
</Routes>
</BrowserRouter>
);
}
First wrap your content into the
Note:
The best way to learn any programming language is to practice more projects. Build small projects and experiment with the concepts.
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