Components | Mastering React: An In-Depth Zero to Hero Video Series

Summary

In this React JS tutorial, the instructor introduces components, the building blocks of React applications, highlighting their reusability. The video explains the difference between functional (stateless) and class (stateful) components. It covers the basics of creating both types, with a focus on the shift towards functional components post-React 16.8 due to Hooks. The instructor demonstrates creating a class component and emphasizes reusability by refactoring an App component and introducing a Student component. The video concludes with a task for viewers to build an application with header, top nav, main, and footer components, and encourages practice with a provided GitHub solution.

Takeaways

• 🎓 This video is part of a 'React JS - Zero to Hero' series aimed at beginners learning React JS from scratch.
• 🔗 The script follows up from a previous discussion on JSX and introduces the concept of components in React.
• 🏗 Components in React are isolated pieces of UI with their own logic and appearance, emphasizing reusability.
• 🧩 There are two types of components in React: Functional Components (Stateless) and Class Components (Stateful).
• 🤖 Functional components are simple JavaScript functions returning JSX, without a render method and no lifecycle methods.
• 📚 Class components are ES6 classes extending React.Component, featuring a render() method and lifecycle phases.
• 📈 The introduction of React Hooks in version 16.8 has led to a preference for functional components over class components.
• 📝 Despite the shift, understanding class components is essential due to their presence in legacy applications.
• 🛠 The video demonstrates creating a class component by extending React.Component and using it within an App component.
• 🔄 The script highlights component reusability by showing how to create and reuse a Student functional component.
• 🔍 The presenter suggests a practice task involving creating a header, top nav, main, and footer component, all reusable within an App component.

Q & A

What are the two main types of components in React?

The two main types of components in React are Functional Components, also known as Stateless components, and Class Components, also known as Stateful components.

What is the primary advantage of using components in React?

The primary advantage of using components in React is reusability, which allows developers to create isolated pieces of UI that can be used multiple times across the application.

How are functional components defined in React?

Functional components in React are typically defined using arrow functions, but they can also be created with the regular function keyword. They are simple JavaScript functions that return JSX.

Why are functional components referred to as 'stateless'?

Functional components are referred to as 'stateless' because they do not have their own state and simply accept data and return JSX based on that data.

What is a Class Component in React and how is it different from a Functional Component?

A Class Component in React is a regular ES6 class that extends the Component class from the React library. It is different from a Functional Component in that it can have its own state and lifecycle methods, and it must implement a render() method that returns JSX.

What is the significance of React Hooks introduced in React 16.8?

React Hooks, introduced in React 16.8, allow developers to use state and other React features in functional components, which has led to a preference for functional components over class components for most use cases.

Why is it important to understand Class Components even though they are less commonly used now?

It is important to understand Class Components because some legacy applications still use them, and having this knowledge can be helpful for maintaining and updating existing codebases.

How do you create a Class Component in React?

To create a Class Component in React, you define a class that extends React.Component, ensure the component's name starts with an uppercase letter, implement a render() method that returns JSX, and export the component for use in other parts of the application.

What is the benefit of creating separate files for components in a React application?

Creating separate files for components in a React application helps in organizing the code better, making it more maintainable and readable, and allows for easier reuse of components.

How can you demonstrate the reusability of components in React?

The reusability of components in React can be demonstrated by creating a component once and then using it multiple times in different parts of the application or even multiple times within the same section of the UI.

What is the next topic the video series will cover after explaining components?

The next topic the video series will cover is passing values dynamically to components, which is essential for creating more flexible and interactive React applications.

Outlines

00:00

📚 Introduction to React Components

This paragraph introduces the concept of components in React, which are isolated pieces of UI with their own logic and appearance. The paragraph explains the two main types of components in React: Functional Components (also known as Stateless components) and Class Components (also known as Stateful components). Functional components are simple JavaScript functions that return JSX and do not have a render method or lifecycle methods, as they are plain JavaScript functions. Class components, on the other hand, are ES6 classes that extend the React component class and must implement a render() method. They also have lifecycle methods associated with different phases such as Mounting, Updating, Unmounting, and Error Handling. The paragraph also discusses the shift towards functional components with the introduction of React Hooks in version 16.8, which has led to a decline in the use of class components. The instructor demonstrates how to create a class component by extending the React component class, implementing a render method, and exporting it for use in other components. The paragraph concludes with a brief mention of the reusability of components, which will be further explained in the next video.

05:02

🔄 Demonstrating Component Reusability

The second paragraph focuses on the reusability of components in React applications. The instructor creates a new functional component called 'Student' using an arrow function and demonstrates how it can be reused multiple times within the 'App' component. This showcases the practical application of component reusability, which is a key advantage of using components in React. The paragraph also hints at future topics, such as passing values dynamically to components, which will be covered in the next video. The instructor concludes by assigning a small task for the viewers to create an application with various components like a header, top nav, main, and footer, and encourages them to style these components using inline styles. The task is designed to help viewers practice what they've learned about components. The paragraph ends with a call to action for viewers to like, subscribe, and support the channel.

Keywords

💡React JS

React JS is a popular open-source JavaScript library used for building user interfaces, particularly for single-page applications. It is maintained by Facebook and a community of individual developers and companies. The video's theme revolves around teaching React JS from scratch, indicating that the content is aimed at beginners who are new to this library. The script mentions building applications with React, highlighting its core role in the tutorial.

💡JSX

JSX is a syntax extension for JavaScript that allows for an HTML-like structure to be used within JavaScript code. It is used in React to describe what the UI should look like. In the script, JSX is mentioned as a topic that was explained in the previous video, suggesting that it's a foundational concept for understanding how to return UI elements in React components.

💡Components

In React, a component is a fundamental building block of the user interface. It represents a part of the screen, and components can contain both UI logic and appearance. The script emphasizes the concept of components as isolated pieces of UI, which can be either functional or class-based, and highlights their reusability as a main advantage.

💡Functional Components

Functional components in React are simple JavaScript functions that return JSX. They are referred to as 'stateless' because they do not manage their own state. The script explains that these components are used for rendering UI based on the data they receive, and they do not have a render method or lifecycle methods, which simplifies their usage for developers.

💡Class Components

Class components in React are created using ES6 classes that extend the React.Component class. They are known as 'stateful' components because they can manage state and have lifecycle methods. The script mentions that class components were the standard way to create components with state and lifecycle logic before the introduction of Hooks in React 16.8.

💡Reusability

Reusability refers to the ability to use a component in multiple places within an application without having to rewrite the code. The script highlights reusability as a key advantage of components in React, showing how the same component can be used multiple times in the UI, which promotes efficiency and maintainability in code development.

💡Lifecycle Methods

Lifecycle methods in React are special methods that are called at specific points in a component's lifecycle. They are used in class components to perform actions such as setting up before rendering (componentDidMount) or cleaning up after a component is unmounted (componentWillUnmount). The script discusses these methods in the context of class components, indicating their importance for managing the component's lifecycle.

💡React Hooks

React Hooks are a feature introduced in React 16.8 that allows state and other React features to be used in functional components. The script mentions that with the introduction of Hooks, developers have started to prefer functional components over class components, as they can now manage state and side effects in a more streamlined way.

💡State

State in React refers to the data that, when changed, can cause a component to re-render. The script discusses state in the context of class components, which are described as 'stateful' because they can implement logic and maintain state. State is a crucial concept for creating interactive UIs that respond to user actions.

💡Props

Props, short for properties, are a way to pass data from one component to another in React. The script mentions that the way events, state, and props are managed differs between functional and class components, indicating that props are a fundamental concept for passing data and functionality down the component tree.

💡Event Handling

Event handling in React refers to the process of responding to user actions, such as clicks or key presses. The script briefly mentions event handling in the context of discussing the differences between functional and class components, suggesting that it is an important aspect of building interactive UIs with React.

Highlights

Introduction to React JS for beginners, focusing on building UI from components.

Explanation of components as isolated pieces of UI with their own logic and appearance.

Advantage of components in React is their reusability.

Differentiation between Functional Components and Class Components.

Functional components are simple JavaScript functions returning JSX.

Functional components are stateless and do not use a render method.

Class components extend the Component class from the React library and are stateful.

Class components must have a render() method that returns JSX.

Lifecycle methods in class components include Mounting, Updating, Unmounting, and Error Handling.

React Hooks introduced in React 16.8, leading to a preference for functional components.

Class components may become deprecated, but understanding them is still necessary for legacy applications.

Step-by-step guide on creating a class component, including naming conventions and importing React.

Demonstration of rendering a class component in the UI.

Introduction to functional components using arrow functions and JSX.

Example of reusing a functional component multiple times in the UI.

Teaching how to pass values dynamically to components, to be covered in the next video.

Assignment for viewers to create an application with a header, top nav, main, and footer component.

Encouragement for viewers to try the task on their own and reference a GitHub repo for solutions.

Call to action for viewers to like, subscribe, and support the channel.

Transcripts

Hi Friends

Welcome back to React JS -  Zero to Hero series. This  

series is for beginners who wants  to learn React JS from Scratch.

In the last video I have explained  about JSX. In this video,  

I am going to explain about components.

Let's start.

React applications are built from isolated  pieces of UI called components. A component  

is a piece of the user interface that  has its own logic and appearance.  

The main advantage of the  component is reusability.

There are mainly two components in  React. Functional Components also  

known as Stateless component. And, Class  Component also known as Stateful component.

Functional components are simple javascript  functions, that returns some JSX. They are  

also called "stateless" components because  they simply accept data and render them in UI.  

There is no render method used in functional  components. Functional components can be  

typically defined using arrow functions but can  also be created with the regular function keyword.  

Component lifecycle method do not  exist in functional component,  

because a functional component is  just a plain JavaScript function.

Even in our previous videos, I have  used functional components only.

Class components are regular ES6 classes that  extends component class form react library.  

They are also known as "stateful" components,  because they implement logic and state.  

It must have a render() method that returns JSX.  There are 4 component lifecycle phases available  

in class components. They are Mounting,  Updating, Unmounting and Error Handling.  

And, in each phase we have different component  lifecycle methods like componentDidMount,  

compondentDidUpdate, componentWillUnmount, etc.

Earlier, react developers prefer to use class  components to create stateful components  

and functional components to create stateless  components. Before React 16.8, Class components  

were the only way to track state and lifecycle  on a React component. But, in React version 16.8,  

React Hooks got introduced. After the introduction  of Hooks, most of the developers prefer to use  

functional components for everything. So,  now-a-days class components are dying slowly.  

In future, those may get deprecated. But I think  there is no official announcement about that.

But still, you need to have an  understanding on class components,  

because some of the legacy applications  are still having class components.

So, let me explain how we  can create a class component.

First let me create a javascript file.  

Inside that, I need to have a class  that should extend react dot component.  

When creating a React component,  the component's name must start  

with an upper case letter. And, we  need to import the react library.

And, the component also requires a  render() method, this method returns JSX.  

Finally, let me export this component,  so that I can use it in other components.

Now, let me go to the index dot js.  And, use the class component there.

So, we can see our class  component is rendering in the UI.

This is how we can create a class component.

The way we call the events, maintain  the state and props, lifecycle methods,  

and other concepts differ between functional  and class components. If I explain both, it  

may confuse you. It takes lot of time to explain  the same concept in both the components. Also,  

as most of the react developers are moving towards  functional components, I am going to mostly use  

only functional components in the upcoming videos.  And, use class components where ever needed.

And, I have told the main advantage  

of the component in react is its  reusability. Let me explain that.

First, let's do some cleanup. In index  dot js, we have the App function.  

Let's move this App function or App component  to a separate file. For that, let me create a  

App dot js file. And, let me move this function  there. Let me also move these imports. And,  

let me export this App component. In index  dot js, let me import the App component.  

I need to move this function also to App  component, because we are using this there only.

Now, our app is still working.  But our index dot js is clean.

Ok. Let me create a new functional  component called Student. This time I am  

going to use arrow function instead of normal  function. And, let me return some JSX inside.

And, I am going to show this  component inside our App component.

So, we can see our student component  is showing in the UI. Assume, you want  

to use the same component in different  places, we can simply use this component.  

Even here, if I want to show it two more  times, I can simply reuse. Like this.

Now, we can see 3 students are showing. This  is what I was telling about reusability.

Ok. Here we are hardcoding some values.  But it will be nice, if we are able to  

pass these values dynamically. That is what  I am going to explain in the next video.

And, let me explain a small task and you can try  that. You can create an application like this,  

in which you need to create a header component,  a top nav component, a main component and a  

footer component. You can use inline styles  to style your components. And, you can use  

all your components inside App component.  So that, it should appear similar to this.

Try it on your own. In case  you need to see the solution,  

you can get it from this github repo.  The link is also in the description.

That's all for today.

Please like this video. Subscribe  my channel and support me.

Thank you. Bye.