17 December 2024 Leave a comment Tech-Help
In the realm of React Hooks, useImperativeHandle, useLayoutEffect, and useDebugValue are tools that may not be frequently employed, but they offer unique functionalities for specific scenarios. This article aims to demystify these hooks and provide practical examples to demonstrate their use cases.
useImperativeHandle
The useImperativeHandle hook is a powerful tool that allows you to customize the instance value exposed to parent components. Typically used with useRef, it provides a mechanism to define what properties or methods a ref will expose.
Example: Imagine you have a custom input component where you want to expose only a specific method, such as a custom blur function. By using useImperativeHandle, you can define this method and control its behavior when accessed from a parent component.
const MyInput = React.forwardRef((props, ref) => {
const [val, setVal] = React.useState('');
const inputRef = React.useRef();
React.useImperativeHandle(ref, () => ({
blur: () => {
document.title = val;
inputRef.current.blur();
}
}));
return (
setVal(e.target.value)}
{...props}
/>
);
});
const App = () => {
const ref = React.useRef(null);
const onBlur = () => {
ref.current.blur();
};
return ;
};
useLayoutEffect
useLayoutEffect is similar to useEffect, but it fires synchronously after all DOM mutations. This makes it ideal for reading layout from the DOM and synchronously re-rendering.
Example: Use useLayoutEffect when you need to measure the layout of a component after an update and apply these measurements to other components.
const Message = ({boxRef, children}) => {
const msgRef = React.useRef(null);
React.useLayoutEffect(() => {
const rect = boxRef.current.getBoundingClientRect();
msgRef.current.style.top = `${rect.height + rect.top}px`;
}, []);
return <span>{children}</span>;
};
const App = () => {
const [show, setShow] = React.useState(false);
const boxRef = React.useRef(null);
return (
<div>
<div> setShow(prev => !prev)}>Click me</div>
{show && Foo bar baz}
</div>
);
};
useDebugValue
The useDebugValue hook is used to display a label for custom hooks in React DevTools. It is particularly useful for debugging custom hooks without impacting performance, as it only runs when the DevTools are open.
While useDebugValue doesn’t directly affect your application’s behavior, it enhances the debugging experience by providing insights into custom hook values.
Enhancing Your Testing Workflow with Repeato
When managing complex React applications, ensuring consistent behavior across different components and states can be challenging. This is where automated testing tools like Repeato come into play. As a no-code test automation tool for iOS and Android, Repeato allows you to create, run, and maintain automated tests for your apps efficiently. Its use of computer vision and AI makes it particularly fast to edit and run tests, ensuring your React Native apps work seamlessly across various scenarios.
