In this article, we will learn about the basic concepts of ReactJS. This article will help you for learning about ReactJS.
There are 10 main concepts for learning ReactJS:
1. Reasons to Learn React Js
Some of the most persistent problems in front-end development have simple answers due to ReactJS. It is quick, scalable, flexible, and powerful, and it has a strong development community that is expanding quickly. The time has arrived to learn about React.
The core ideas of React, including JSX, class and function components, props, state, lifecycle functions, and hooks, will become deeply ingrained in your mind. These concepts can be merged using React’s modular programming approach.
React is not a framework:
There are frameworks, like Angular or Ember, that have certain decisions already made for you. React is basically a library, and you are responsible for all decision-making. It focuses on supporting you in using components to build user interfaces.
2. JSX expressions
Anywhere in JSX, you can use a pair of curly brackets to include a JavaScript expression:
JSX nesting elements:
const myClasses = (
<a href="https://www.letsreact.org">
<h1> Login! </h1>
</a>
);A JSX expression must have exactly one outermost element in order for the code to compile. The <a> tag is the outermost element in the block of code below.
SX is a JavaScript syntactic extension. The DOM elements it produces are then rendered in the React DOM.
Before it enters a web browser, a JavaScript file containing JSX must be built. A sample of compilable JavaScript code is shown in the code block.
3. React Virtual DOM
The term “Virtual DOM” must be familiar to everyone using or learning React. Why does React use a Virtual DOM, and what is it?
The virtual DOM (VDOM) is a programming concept in which a library like ReactDOM maintains an ideal, or “virtual,” representation of a user interface in memory and keeps it in sync with the “actual” DOM. Reconciliation is the term used to describe this process.
This strategy makes React’s declarative API possible: React works to ensure that the DOM conforms to the state you specify for the UI. This abstracts out the manual DOM updates, event handling, and attribute manipulation that you would normally need to utilize to create your app.
This is where the idea of virtual DOM is useful because it outperforms real DOM by a wide margin. Only a virtual representation of the DOM exists in the virtual world. The virtual DOM is updated rather than the real DOM each time the state of our program changes.
Perhaps you’re saying to yourself, This seems like double labor. Isn’t the virtual DOM performing the same thing as the real DOM? How is this any quicker than simply refreshing the actual DOM?
The short answer is that virtual DOM is much faster and more effective.
Why is Virtual DOM faster?
A virtual DOM, which is seen as a tree, is produced when new UI elements are added. Each component of this tree is a node. A new virtual DOM tree is constructed whenever the state of any of these items changes. The following virtual DOM tree is “diffed” or compared to this one.
Following this, the virtual DOM determines the most effective way to make these modifications to the real DOM. This guarantees that minimal operations are made to the real DOM. Consequently, updating the real DOM requires less processing power.
4. Using Virtual DOM in React
Let’s look at how React uses the virtual DOM now that you have a basic knowledge of what it is and how it might improve the performance of your project.
Each UI element in React is a separate component with its own state.. React watches for state changes and adheres to the observable pattern. Every time the state of a component changes, React changes the virtual DOM tree. React then compares the most recent and earlier versions of the virtual DOM once the virtual DOM has been changed. This procedure is known as “diffing.”
In simple words, you tell React what state you want the user interface to be in, and it ensures that the DOM reflects that state. As a developer, you would not need to understand how to attribute manipulation, event handling, or manual DOM modifications take place behind the scenes, which is a massive benefit.
Developers using React are shielded from all of these details. You only need to alter the component’s states as and when necessary; React takes care of the rest. This ensures a better development experience using React.
5. Props in JSX
Properties, which refer to an object’s properties, are referred to as props in React. This is due to the fact that all React elements are JavaScript objects. As a result, defining attributes and values for the object are how data is passed into a component.
Due to the peculiar way React functions, it can be difficult to understand how to use props at first. React props are read-only, meaning that the data cannot be altered once it has been supplied to a component.
It might sound like it severely restricts how you can utilize props in your React code. However, it actually isn’t; in fact, it strengthens both security and performance. Props function by sending information to a component, which is commonly used for UI requirements.
6. The components of ReactJS
One of React’s fundamental building blocks is the component. Or, to put it another way, every application you create with React will be built up of what are known as components. Using components makes creating user interfaces considerably simpler. You can see a user interface (UI) divided into numerous separate parts, or components, and work on them independently before merging them all into a parent component to create your final UI.
React’s components are divided into two categories:
a) Functional Components
Javascript functions are the basic minimum of functional components. By writing a javascript function, we can build a useful React component. As we shall discuss later in the lesson, these functions may or may not accept data as parameters. A functional component in React is demonstrated in the example below:
const Demo =()=>
{
return <h1>Hello Rohit!</h1>;
}b) Class Components:
Compared to functional components, class components are a little more sophisticated. While the class components can cooperate with one another, the functional components in your application are unaware of the other components. Data can be passed from one class component to another. To develop class-based components for React, we can use JavaScript ES6 classes. A React component that uses classes is demonstrated in the example below:
class Demo extends React.Component
{
render(){
return <h1>Hello Rohit!</h1>;
}
}7. React Props And PropTypes
We’ll go into great detail on props and prototypes because they’re a crucial method for passing data between React components. The specifics of props, passing and accessing props, and sending data to any component via props will be covered in this course. However, utilizing PropTypes to check the data we are receiving through props is always a smart idea. As a result, you will also discover how to include PropTypes in React.
React allows us to use objects called props to pass information to components (short for properties). Props enable sharing of the same data across the various components that make up React because they all require it. It uses a one-way data flow system (parent-to-child components). However, it is possible to transfer props back from a child component to a parent component via a callback method.
Numerous formats, including numbers, texts, arrays, functions, objects, etc., are possible for these data. Just like we can specify attributes in any HTML tag, we can give props to any component. Look at the code in the following:
<TodoList todos={todosList} />In this sample, a component called TodoList is receiving a prop called posts as a parameter. The value of this prop is “todosList.” Let’s examine the accessing and passing of data.
8. Performance Optimization for React Apps
React has changed the way front-end developers create online applications since it was first released, and its virtual DOM is renowned for efficiently rendering components. This lesson will cover several performance optimization techniques for React applications as well as React’s speed-enhancing capabilities.
React creates a DOM tree of components during the initial rendering process. Therefore, we want React to re-render only those components that were affected by the change and bypass the remaining components in the tree that were not affected when data in the DOM tree changes.
Even if not all DOM tree elements are touched, React can wind up re-rendering all of them. Longer loading times, lost time, and possibly even wasted CPU resources will be the effect of this. This needs to be stopped, please. We shall therefore concentrate our optimization efforts here.
9. State in React
The state is a structure that can be updated and is used to store data or details about the component. A component’s status may alter over time. A user action or a system event may cause the status to change over time. Stateful components are components that have a state. The react component’s core controls the component’s functionality and rendering. Additionally, they are in charge of giving a component life and interaction.
A state must remain as straightforward as feasible. It can be changed by calling the setState() method, a process that causes UI updates. The local state or data of a component is represented by a state. Only the component itself or the component itself can access or modify it. We must utilize the getInitialState() method to set an initial state before any interaction takes place.
10. Hooks of React
Hooks is the name of the new functionality that was added to React 16.8. You can use state and other React features without creating a class. Hooks are the functions that allow function components to “hook into” state and lifecycle elements of the React framework. In a classroom, it is ineffective.
Since Hooks are backward-compatible, they don’t include any fundamental changes. It also doesn’t take the place of your understanding of React ideas.
How and When to Use Hooks
In order to add a state to a function component that you have written, you must first turn it into a class. However, you can now accomplish it by utilizing a Hook inside the current function component.
Hooks’ Rules
Although hooks and JavaScript functions are similar, employing them requires that you adhere to these two guidelines. All stateful functionality in a component must be visible in the source code, thanks to the hooks rule. These guidelines are:
- Only use Hooks at the highest level.
Hooks should not be called inside of loops, conditions, or nested functions. The top level of React functions should always use hooks. This rule makes sure that Hooks are called every time a component renders in the same order. - Only use Hooks when calling React functions
Regular JavaScript functions cannot call Hooks. Instead, you can use the React function components to call Hooks. Furthermore, custom Hooks may call hooks.
Conclusion
This article will help you to learn about React concepts. Thank you for reading my article. Hope you understand very well. Happy learning!
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