Size-Aware React Components

Size-Aware Components in React: A Comprehensive Guide

When building React applications, it’s often essential for components to be aware of their size and position on the screen. This knowledge is crucial for rendering content correctly, handling size changes, and creating responsive layouts. In this article, we’ll explore two excellent libraries that help solve this problem: react-measure and react-sizeme.

The Importance of Size Awareness

Components need to know their size and position to handle various scenarios, such as:

• Responsive layouts that change from one to two columns or switch to a hamburger menu when width-constrained
• HTML5 Canvas elements that require redrawing when their size changes
• Adjustable pane sizes in a layout
• Elements or third-party libraries that require a known size, like react-virtualized or fixed-data-table
• Absolute positioning that needs adjusting when the container size changes
• Animating an element’s size with CSS and additional logic that depends on this animated size

Introducing react-measure

react-measure is a helpful library for building size-aware components. It wraps a component and exposes an onResize function that is called with the element’s contentRect (which has bounds and position). This method is called whenever the component’s size or position changes, allowing you to trigger side effects or update the component’s state.

However, there’s a chicken-and-egg problem: when the component renders for the first time, its dimensions aren’t always known since its width and height could be determined by its content.

Solving the Chicken-and-Egg Problem with react-sizeme

react-sizeme is similar to react-measure but uses a clever solution to solve the aforementioned problem. It performs an initial, invisible render of the component to measure its size in a lightweight way. Then, when the component renders, the size is known, and the component can render properly from the beginning.

Using react-sizeme looks like this:
“`jsx
import { SizeMe } from ‘react-sizeme’;

const MyComponent = () => {
const { width, height } = useSize();

return (

);
};

const App = () => {
return (



);
};
“`
Caveats and Performance Considerations

Both libraries have some caveats to be aware of:

• The initial render that react-sizeme performs to determine the component’s dimensions isn’t free and can increase the time to visibility of a rendered component.
• The methods used to detect size changes have a slight latency (~20ms), which can lead to a component feeling slow.

In general, react-measure has less of a performance impact, so it should be used if possible. However, in cases where a component’s initial render depends on its size, react-sizeme is a good option.

By understanding the importance of size awareness and using the right library for your needs, you can create more responsive, efficient, and effective React applications.