Rendering Elements and Components

Rendering elements and components is an important part of building applications with React. In this article, we will explore the different ways to render elements and components in React and how to choose the best option for your needs.

Rendering Elements

In React, an element is a plain object that represents a DOM element. Elements are the smallest building blocks of a React application, and they are created using the React.createElement() function.

For example, consider the following element that represents a div element:

const element = 
React.createElement('div', {}, 'Hello, world!');

In this example, the React.createElement() function creates a new element based on the tag name, props, and children that are passed to it. The first argument is the tag name, the second argument is the props object, and the third argument is the children of the element.

To render an element to the DOM, you need to pass it to the ReactDOM.render() function. The ReactDOM.render() function takes the element as an argument and renders it to the specified DOM node.

For example, consider the following code that renders the element to the root DOM node:

ReactDOM.render(element, 
document.getElementById('root'));

In this example, the element is rendered to the root DOM node, and it will be displayed as a div element with the text “Hello, world!” inside.

Rendering elements is a simple and efficient way to update the UI of a React application, but it has some limitations. Elements are static and cannot be modified once they are created, so they are not suitable for dynamic and interactive UI.

Rendering Components

To create dynamic and interactive UI in React, you need to use components. A component is a reusable and modular piece of code that represents a part of the UI. Components can be either functional or class-based, and they are created using the React.createElement() function or the React.Component class.

For example, consider the following functional component that represents a Button:

import React from 'react';

function Button(props) {
  return (
    <button onClick={props.onClick}>
      {props.label}
    </button>
  );
}

In this example, the Button component is a functional component that returns a button element with an onClick prop and a label prop. The onClick prop is a callback function that is called when the button is clicked, and the label prop is the text that is displayed on the button.

To render a component to the DOM, you need to pass it to the ReactDOM.render() function just like you would with an element. The component will be rendered to the specified DOM node and will be updated whenever the component’s state or props change.

For example, consider the following code that renders the Button component to the root DOM node:

ReactDOM.render(<Button label="Click me" 
onClick={() => alert('Hello, world!')} />, 
document.getElementById('root'));

In this example, the Button component is rendered to the root DOM node, and it will be displayed as a button with the text “Click me”. When the button is clicked, an alert with the text “Hello, world!” will be displayed.

Rendering components is a powerful and flexible way to create dynamic and interactive UI in React, and it is the most commonly used way to build applications with the framework.

Choosing Between Elements and Components

When building applications with React, you need to decide whether to use elements or components to render your UI. Elements are simple and efficient, but they are static and cannot be modified once they are created. Components are more powerful and flexible, but they are more complex and require more setup.

As a general rule, you should use elements for simple and static UI, and you should use components for dynamic and interactive UI. For example, you might use elements for displaying simple text or images, and you might use components for displaying forms or interacting with APIs.

Conclusion

By understanding the strengths and limitations of elements and components, you can choose the best option for your needs and build scalable and maintainable applications with React.

Exercises

To review these concepts, we will go through a series of exercises designed to test your understanding and apply what you have learned.