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Supermarket Belongs to the Community

Supermarket belongs to the community. While Chef has the responsibility to keep it running and be stewards of its functionality, what it does and how it works is driven by the community. The chef/supermarket repository will continue to be where development of the Supermarket application takes place. Come be part of shaping the direction of Supermarket by opening issues and pull requests or by joining us on the Chef Mailing List.

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React Portals in Functional Components: A Comprehensive Guide DSC Resource

In this comprehensive guide, we will delve into the world of React Portals and explore how they can be used with functional components.

Install & Usage Instructions

React, with its declarative and component-based architecture, has revolutionized the way we build user interfaces for web applications. While React offers a straightforward way to create reusable components, there are scenarios where you need to render elements outside the normal component hierarchy. This is where React Portals come into play, allowing you to render components outside their parent hierarchy and often proving essential for building sophisticated UIs.

In this comprehensive guide, we will delve into the world of React Portals and explore how they can be used with functional components. You'll learn what React Portals are, why they are valuable, and how to implement them effectively in your React applications. By the end, you'll have a deep understanding of this powerful feature and how to leverage it in your projects.

What are React Portals?

React Portals provide a way to render elements outside the DOM hierarchy of their parent components. In simpler terms, they allow you to insert a React component's subtree into a different part of the DOM, even if it's not a direct child of that component. This feature comes in handy when you need to create UI components that are visually connected to a part of the page but aren't constrained by the layout or styling of their parent components.

Why Use React Portals?

React Portals serve several crucial purposes in modern web development:

Accessibility: Portals enable developers to create accessible UI components such as modals, tooltips, and context menus. These components can be rendered outside the parent component hierarchy but remain semantically associated with the triggering element.

Separation of Concerns: Portals allow for a clean separation of concerns. UI components like modals and popovers can be implemented independently, making code easier to maintain and test.

Styling and Positioning: Portals grant full control over the styling and positioning of UI elements. This is particularly useful when creating overlays or dropdowns that need to be positioned precisely.

Avoiding Z-Index Issues: Portals can be used to avoid z-index conflicts. Since portal content is rendered at a higher level in the DOM hierarchy, it can easily appear above other elements without complex z-index management.

Now, let's explore the fundamentals of React Portals.

The Basics of Portals

Creating a Portal: Creating a portal in React is straightforward. You start by importing the ReactDOM library and use the createPortal function it provides. Here's a basic example:

import React from 'react';
import ReactDOM from 'react-dom';

const Modal = ({ children }) => {
return ReactDOM.createPortal(
document.getElementById('modal-root') // The target DOM element
export default Modal;

In this example, we've created a Modal component that uses ReactDOM.createPortal to render its children to a DOM element with the id modal-root. This DOM element should be present in your HTML file, typically at the end of the <body>.

Portal Destination: The destination element you specify when creating a portal determines where the portal content will be rendered. This is usually a div or another container element in your HTML file. Make sure this destination element exists before attempting to render your portal.

Here's a sample HTML structure:

<!DOCTYPE html>


With the basics covered, let's explore how React Portals can be used effectively with functional components.

Functional Components and Portals

Using Portals in Functional Components: Functional components, introduced in React as part of the Hooks API, have gained popularity for their simplicity and composability. React Portals work seamlessly with functional components, allowing you to create UI elements that are both powerful and easy to maintain.

Here's an example of using a portal with a functional component:

import React, { useState } from 'react';
import ReactDOM from 'react-dom';

const Modal = ({ isOpen, onClose, children }) => {
if (!isOpen) return null;

return ReactDOM.createPortal(
<div className="modal">
<div className="modal-content">
<button onClick={onClose}>Close</button>

const App = () => {
const [modalIsOpen, setModalIsOpen] = useState(false);

const openModal = () => {

const closeModal = () => {

return (
<button onClick={openModal}>Open Modal</button>
<Modal isOpen={modalIsOpen} onClose={closeModal}>
<h2>Modal Content</h2>
<p>This is a modal dialog.</p>

ReactDOM.render(<App />, document.getElementById('root'));

In this example, the Modal component is a React portals functional component that uses a portal to render its content outside the parent component hierarchy. The isOpen prop controls whether the modal is visible, and the onClose prop allows you to close the modal.

Benefits of Functional Components

Using functional components with React Portals offers several advantages:

Simplicity: Functional components are concise and easy to read, making your codebase more maintainable.

Hooks: Functional components can take full advantage of React's Hooks API, allowing you to manage state and side effects effortlessly.

Composition: Functional components encourage component composition, promoting a modular and reusable code structure.

Now that we understand how to use portals with functional components, let's explore some common use cases for React Portals.

Common Use Cases

React Portals are incredibly versatile and can be used in various scenarios. Here are some of the most common use cases:

Modals and Dialogs: Modal dialogs are a classic use case for portals. They appear on top of the main content, allowing users to interact with them while temporarily blocking access to the rest of the application. Modals are commonly used for tasks like login forms, image previews, or confirmation dialogs.

Tooltip Popovers: Tooltips and popovers are UI elements that display additional information when a user interacts with a specific element. Portals make it easy to position and style tooltips and popovers precisely. You can create reusable tooltip components that work seamlessly across your application.

Context Menus: Context menus are menus that appear when a user right-clicks on an element. They often contain options relevant to the clicked element. Portals enable you to create context menus that can be positioned near the cursor, providing a better user experience.

Notification Popups: Notification popups, such as success messages, error alerts, or in-app notifications, can be implemented using portals. These popups can appear at the top or bottom of the screen, outside the regular layout, and disappear after a short time.

Now, let's explore advanced techniques for working with React Portals.

Advanced Techniques

Event Handling: When using React Portals, you might need to handle events that occur outside the portal content. For example, you may want to close a modal when a user clicks outside of it. This can be achieved by attaching event listeners to the document object and handling the events accordingly.

Here's an example of closing a modal when the user clicks outside of it:

import React, { useEffect } from 'react';
import ReactDOM from 'react-dom';

const Modal = ({ isOpen, onClose, children }) => {
useEffect(() => {
const handleOutsideClick = (event) => {
if (isOpen && !modalContentRef.current.contains( {

document.addEventListener('mousedown', handleOutsideClick);

return () => {
  document.removeEventListener('mousedown', handleOutsideClick);

}, [isOpen, onClose]);

if (!isOpen) return null;

const modalContentRef = useRef(null);

return ReactDOM.createPortal(
<div className="modal">
<div className="modal-content" ref={modalContentRef}>
<button onClick={onClose}>Close</button>

In this example, we attach a mousedown event listener to the document object to detect clicks outside the modal. When a click occurs outside the modal content, the onClose function is called to close the modal.

Nesting Portals: Portals can also be nested, allowing you to create complex UI structures. For instance, you can have a modal that contains another portal-rendered component, such as a dropdown menu or a tooltip.

To nest portals, simply create a new portal within the children of an existing portal component. Ensure that each portal has its destination element to prevent conflicts.

Portal with State Management: When using portals with state management libraries like Redux or Mobx, it's essential to ensure that the state remains consistent. Changes in one part of your application can trigger portal components to update. Be mindful of how you manage and share state between different parts of your application when using portals.

Testing React Portals

Testing components that use portals can be challenging due to the rendering of elements outside the component hierarchy. However, various testing strategies and libraries can help you write effective tests for portal components.

Testing Strategies

When testing components with portals, consider the following strategies:

Integration Testing: Integration tests verify that components work correctly together. They ensure that portals render content in the expected destinations and that interactions trigger the desired behavior.

Snapshot Testing: Snapshot testing captures the rendered output of a component and compares it to a previously saved snapshot. This can help detect unexpected changes in the component's appearance.

DOM Testing: Libraries like React Testing Library or Enzyme can be used to query the DOM and interact with portal components as if they were part of the regular component hierarchy.

Tools and Libraries

To assist with testing portal components, you can use testing libraries and utilities designed for React. Here are some popular options:

React Testing Library: This library focuses on testing components as they would be used by end-users. It provides a simple and intuitive API for querying and interacting with your components.

Enzyme: Enzyme is a testing utility for React that provides a shallow rendering option, which can be useful when testing components that use portals. Shallow rendering doesn't render child components deeply, making it easier to isolate the component being tested.

Jest: Jest is a popular testing framework for JavaScript that can be used in conjunction with testing libraries like React Testing Library or Enzyme to write and run tests for portal components.


In this comprehensive guide, we've explored the world of React Portal and their integration with functional components. We began by understanding what React Portals are and why they are essential in modern web development. React Portals offer a powerful solution for rendering elements outside the normal component hierarchy, enabling the creation of complex and user-friendly UI components.

We covered the basics of portals, including how to create them and specify their destination in the DOM. We also learned how to effectively use React Portals in functional components, taking advantage of the simplicity and composability they offer.

Whether you're starting a new project or need assistance with an existing one, CronJ can provide the expertise and support you need to achieve your goals. With their expertise in React and modern web technologies, CronJ ReactJS development company can help you turn your ideas into reality and deliver exceptional user experiences to your audience.


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