React.js

Start Your React Journey | A Step-by-Step Guide.

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12 months ago

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In this guide, you’ll learn about React JS, a lightweight tool for writing code quickly and efficiently. Here are some key things you’ll find out:

  • Develop Dynamic Web Applications

With ReactJS, building web apps that change and respond is easier. You can show different parts of a webpage without writing complicated code.

  • Code Maintainability

ReactJS helps you write code that’s easier to understand and use again. This means you spend less time fixing things and more time making your app better.

  • Mobile App Development

You can use ReactJS to build apps for mobiles, too. It works well for both Android and IOS, so you can make apps that look good and work smoothly.

What is React and Why use ReactJS

React is a popular tool used in developing websites. It’s a library that helps developers build the parts of websites that users see and interact with. Big companies like Netflix and Instagram use React for their websites.

ReactJS helps make websites faster and smoother by using something called virtual DOM. This means that when things change on a website, React only updates the parts that need to change, instead of updating everything. This makes websites feel quicker and more responsive to users.

Here’s a simplified breakdown of the features of ReactJS

  1. JSX: JSX is an extension of ReactJS that’s not mandatory but incredibly useful. It makes writing code easier by allowing JavaScript and HTML to be written together.
  2. Components: Components are like simple JavaScript functions. They help in organizing code by breaking it into reusable chunks. Components can be used as functions or classes, and they have properties and states to manage data.
  3. Virtual DOM: React creates a virtual DOM, which is like a temporary storage for changes in the web page. This helps in making updates faster because React only updates what’s necessary in the actual web page (DOM) instead of re-rendering everything.
  4. JavaScript Expressions: In JSX files, you can use curly brackets to insert JavaScript expressions. This makes it easy to include dynamic content within your code.

1. JSX

JSX is like a special language that lets us write HTML tags right inside our JavaScript code when we’re working with ReactJS. It makes building web pages with React easier. Here’s an example:

Let’s say we want to make a button that says “Click me” and does something when clicked. With JSX, we can write it like this:

import React from 'react';

const Button = () => {
  return (
    <button onClick={() => console.log('Button clicked!')}>
      Click me
    </button>
  );
}

export default Button;

Without JSX, the above code would look like this:

import React from 'react';

const Button = () => {
  return React.createElement('button', { onClick: () => console.log('Button clicked!') }, 'Click me');
}

export default Button;

2. Components

Components in ReactJS are like building blocks for web pages. They help in organizing and reusing code, making it easier to create complex user interfaces. Each component can have its own look, behavior, and data.

Here’s a simple example of a greeting component:

import React from 'react';

const Greeting = (props) => {
  return (
    <div>
      <h1>Hello, {props.name}!</h1>
      <p>Welcome to CodeSick.</p>
    </div>
  );
}

export default Greeting;

In this component, We define a component called “Greeting”.
It takes a “name” property as input (passed through “props”).
Inside, we use JSX to structure the greeting message, including the “props.name” to personalize it.

3. Virtual DOM

What is Virtual DOM in ReactJS?

Virtual DOM is a concept used in ReactJS to improve the performance of web applications. It is like a lightweight copy of the actual DOM (Document Object Model) of a web page. Instead of directly interacting with the real DOM every time the UI changes, React updates the Virtual DOM first.

How does it work?

When you make changes to your web page using React, such as adding or updating elements, React does not immediately update the actual DOM. Instead, it first makes those changes to the Virtual DOM. Then, it compares the virtual DOM with the real DOM and identifies the most efficient way to update the real DOM to reflect the changes.

Example: Suppose you have a list of items on a web page. You want to add a new item to the list using React.

  1. first updates the Virtual DOM with the new item added to the list.
  2. Then, it compares the updated Virtual DOM with the real DOM to see what has changed.
  3. Finally, React only updates the actual DOM section as opposed to updating the entire list.

This process of first updating the Virtual DOM and then selectively updating the actual DOM is much faster and more efficient than manipulating the actual DOM directly every time it changes.

Simply, Virtual DOM helps make web applications faster and more responsive by minimizing unnecessary updates to the actual web page.

4. JavaScript Expressions

JavaScript expressions in ReactJS allow us to include dynamic content within our JSX code. We use curly braces “{}” to embed JavaScript expressions directly into our JSX.

Example: Displaying a Variable

Let’s say we have a variable “name” that holds a person’s name. We want to display this name within our JSX code:

import React from 'react';

const Greeting = () => {
  const name = 'Sandun';

  return (
    <div>
      <h1>Hello, {name}!</h1>
      <p>Welcome to CodeSick.</p>
    </div>
  );
}

export default Greeting;

In this example, We define a variable “name” with the value ‘Sandun’.
Inside the JSX code, we use curly braces “{}” to include the “name” variable within the greeting message. This allows us to dynamically display the person’s name.

Using JavaScript Expressions

JavaScript expressions can include any valid JavaScript code, such as variables, functions, arithmetic operations, and more. They are evaluated and inserted into the JSX when the component is rendered.

JavaScript expressions in ReactJS make it easy to create dynamic and interactive user interfaces by incorporating dynamic data directly into our JSX code.

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