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Essential things to know as React Developer

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React is an open-source JavaScript library used to create user interfaces in a declarative and efficient way. It is a component-based front-end library responsible only for the view layer of a Model View Controller(MVC) architecture. React is used to create modular user interfaces and promotes the development of reusable UI components that display dynamic data. This article covers all the essential topics provided by ReactJS which every developer should know.

1. Why we should learn React ?

React has become one of the most popular JavaScript library of fronend development. It provides fast, scalable web app building capabilities. It has a huge community and fulfilled with lots of inbuild and 3rd parties libraries and packages which makes it a complete frontend development package.

React has lots of features like JSX (which makes it able to write HTML and CSS in JavaScript), class and function components, props, state, lifecycle methods, hooks, etc. We can combine all these features in React’s modular programming style.

Note: It’s not a framework

It is a misconception between many developers that React is a framework but unlike Angular, Vue etc. React is not a framework but a library.

In framework there is predefined rigid structure of the application whereas in React there is a flexibility to make all the decision for the development by yourself.

2. JSX and its expressions.

JSX, or JavaScript XML, is an extension to JavaScript used in React to explain the UI components. It looks likes HTML but allows embedding JavaScript expressions inside curly braces. JSX provides a concise and readable way to create React Application.

Under the hood, JSX gets compiled into JavaScript function. It simplifies the method of writing React components through combining HTML-like syntax with the ability of JavaScript expressions. JSX resembles HTML, allows you to write familiar code for developing UI components.

Syntax:

const imgUrl = 'example.jpg';
const element = <img src={imgUrl} alt="Example" />;

3. React Virtual DOM

Virtual DOM is one of the crucial feature of ReactJS which makes it really fast. The Virtual DOM is a lightweight copy of actual DOM maintained by React. Every time the state of our application changes, the virtual DOM gets updated instead of the real DOM.

Does it inhances performance?

When new elements are added or any changes happens to the UI, a virtual DOM, which is represented as a tree is created. Each element is assigned as a node on this tree. If the state of any of these elements changes, a new virtual DOM tree is created. This tree is then compared with the previous virtual DOM tree. Later the virtual DOM calculates the best possible method to make these changes to the real DOM. This helps to do minimal operations on the real DOM which reduces the performance cost of updating the real DOM.

4. Props and State in React

In React, both props and state are essential concepts which are used to manage and control the behavior and appearance of components.

Props or properties are used to pass data between the components (parent to child, child to parent, between siblings etc.). They are immutable which means they can’t change only they can be passed. It provides a way to make components reusable by allowing the parent to configure the child components.

Example:

Javascript




// Parent Component
const ParentComponent = () => {
    return <ChildComponent name="John" age={25} />;
};
 
// Child Component
const ChildComponent = (props) => {
    return (
        <div>
            <p>Name: {props.name}</p>
            <p>Age: {props.age}</p>
        </div>
    );
};


State helps make the React application dynamic and allows for updates based on requirements. Unlike props, state can be modified within the component using its setState function, triggering re-renders to reflect the updated state.

Example:

Javascript




const Counter = () => {
    const [count, setCount] = React.useState(0);
 
    const incrementCount = () => {
        setCount(count + 1);
    };
 
    return (
        <div>
            <p>Count: {count}</p>
            <button onClick={incrementCount}>Increment</button>
        </div>
    );
};


5. Components in React

In React, Components are the building blocks which are used to create reusable code of user interface. They can be seen as independent and isolated functions or classes responsible for rendering a part of the UI. In React there are two types of components.

  • Functional Components: Functional components are some of the more common components that will come across while working in React. These are simply JavaScript functions. We can create a functional component to React by writing a JavaScript function.

Example:

Javascript




// Functional Component with useState hook
const Counter = () => {
    const [count, setCount] = React.useState(0);
 
    const incrementCount = () => {
        setCount(count + 1);
    };
 
    return (
        <div>
            <p>Count: {count}</p>
            <button onClick={incrementCount}>Increment</button>
        </div>
    );
};


  • Class Components: The class components are a little more complex than the functional components. The functional components are not aware of the other components in your program whereas the class components can work with each other. We can use JavaScript ES6 classes to create class-based components in React.

Example:

Javascript




class Counter extends React.Component {
    constructor(props) {
        super(props);
        this.state = { count: 0 };
    }
 
    render() {
        return (
            <div>
                <p>Count: {this.state.count}</p>
                <button onClick={() => this.setState({
                                                count: this.state.count + 1
                                       })}>
                    Increment
                </button>
            </div>
        );
    }
}


6. State Management in React

State management in React refers to the handling and control of data within components which allows for dynamic updates, re-rendering, and synchronization of user interfaces based on changes in data. There are several ways by which you can manage the state in React.

  • Using React Hooks (useState, useReducer) in functional component and by using setState in class based component you can easily manage the state. Each component manages its own state, allowing for encapsulation and isolation of data within that specific component.
  • Redux, an open-source JavaScript library, is a versatile tool of ReactJS to manage complex application state. Building Parts of redux are Action, Reducer and Store.
  • The React Context API provides a way to share state data across the component tree without passing props through every level. It is done by storing the props in a store and allows child components to access these props from the store without the need for manual passing at each level of the component tree.

7. React Hooks

Hooks are used to give functional components an access to use the states and are used to manage side-effects in React. They were introduced React 16.8. They let developers use state and other React features without writing a class For example- State of a component It is important to note that hooks are not used inside the classes.

Some of the React Hooks are useState, useEffect, useReducer, useMemo, useCallback, useRef etc.

8. Performance

There are various factors and aspects which are used to improve performance in React which ensure efficient rendering, smooth user interactions, and minimal resource consumption. Some of the key strategies to enhance React app performance:

A. Virtual DOM: React uses Virtual DOM which helps to increase performance of the application. Every time the state of our application changes, the virtual DOM gets updated instead of the real DOM.

B. State and Props Management: Use state effectively and avoid unnecessary re-renders by only updating state when needed. Avoid passing excessive or unnecessary props down the component tree to prevent unnecessary re-rendering of components.

C. Lazy Loading: It refers to a technique which is used to increase performance by loadingcomponenets or assets only whenever required rather than loading everything at a time.

D. Memoization: Use memoization techniques (e.g., useMemo, useCallback) to cache computations and to prevent recalculation of values on each render.

9. Lifecycle Methods in React

In React lifecycle of components starts from its initialization and ends when it is unmounted from the DOM. Every React Component has a lifecycle of its own, lifecycle of a component can be defined as the series of methods that are invoked in different stages of the component’s existence.

Component can go through four stages of its life as follows. 

  • Initialization: This is the stage where the component is constructed with the given Props and default state. This is done in the constructor of a Component Class.
  • Mounting: Mounting is the stage of rendering the JSX returned by the render method itself.
  • Updating: Updating is the stage when the state of a component is updated and the application is repainted.
  • Unmounting: As the name suggests Unmounting is the final step of the component lifecycle where the component is removed from the page.

10. Conditional Rendering

Conditional rendering in React means displaying different components or content based on certain conditions. There are various methods by which it can be achieved in React like if-else statement, Logical && Operator, Ternary Operator, Logical OR Operator, Switch Statements etc.

Example:

Javascript




//using if-else
 
const MyComponent = ({ isLoggedIn }) => {
    if (isLoggedIn) {
        return <LoggedInComponent />;
    } else {
        return <LoginComponent />;
    }
};
 
// using && operator
 
const MyComponent = ({ isLoaded }) => {
    return isLoaded && <LoadedComponent />;
};
 
//using ternary operator
 
const MyComponent = ({ hasError }) => {
    return (
        <div>
            {hasError ? <ErrorComponent /> : <RegularComponent />}
        </div>
    );
};
 
//using logical or operator
 
const MyComponent = ({ name }) => {
    return (
        <div>
            <h1>Welcome, {name || 'Guest'}!</h1>
        </div>
    );
};
 
//using Switch statement
 
const renderContent = (selectedTab) => {
    switch (selectedTab) {
        case 'tab1':
            return <Tab1Content />;
        case 'tab2':
            return <Tab2Content />;
        default:
            return <DefaultContent />;
    }
};




Last Updated : 01 Jan, 2024
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