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Check if the input value is a valid number in React: Check if the input value is not an empty string or contains only spaces. Pass the value to the isNaN() function. If isNaN returns false , then the value is a valid number. import {useState} from rea...

There are multiple reasons why the Component cannot be used as a JSX component error appears: Returning an array of JSX elements instead of a single element. Returning any value other than a JSX element or null from a component. Having an outdated ver...

To create an input field that contains only allowed numbers using React.js: Set the input field's type to text. Add an onChange event handler that removes all non-numeric values. Save the input value in a state variable. import {useSt...

Passing functions as props in React TypeScript: Define the type of the function property in the component's interface. Define the function in the parent component. Pass the function as a prop to the child component. interface ButtonProps { sum : ( a: ...

When we pass a value that is not a function to the onClick attribute of an element, we get the error Expected onClick listener to be a function . To fix the error, make sure you only pass a function to the onClick attribute of an element. const App = ...

We can export multiple components in React using named exports, such as export function A() {} and export function B() {} . We can import the exported components using named imports, such as import {A, B} from ./another-file . We can use the same name...

When two or more elements returned from the map() method have the same key property, a React error Encountered two children with the same key will occur. To fix this error, you need to provide a unique value for the key prop of each element or use ind...

To check if a prop was passed to a component in React: Compare the prop to undefined. If the prop is equal to undefined, then it was not passed to the component. Otherwise, it was passed to the component. const Button = ({withIcon}) = { if...

To clear a timeout or interval in React using hooks: Use the useEffect hook to set a timeout or interval. Return a function from the useEffect hook. Use the clearTimeout() or clearInterval() method to remove the timeout when the component unmounts. , ...

To type the useState hook in React as an array of strings, use the hook's generics, such as const [names, setNames] = useStatestring[]([]) . State variables can be initialized to an empty array or an array of strings, and only accept string values....

When a component returns multiple elements, you get the React.js error JSX expression must have a parent element. To fix the error, wrap the elements in a parent div element or use fragments, such as h2One/h2h2Two/h2/ . Below is an example that produc...

The error React hook useEffect is called conditionally occurs when we use the useEffect hook conditionally or after a condition that may return a value. To fix the error, move all React hooks above any condition that may return a value....

To get the value of an input field using ref in React: Set the ref attribute on the input element. Access the value of the input field on the ref object, e.g. ref.current.value . import { useRef } from react ; const App = () = { const inputRef = useRe...

When we use a string as a reference in a function component, we get the error Function components cannot have string refs. To fix the error, use the useRef() hook to get a mutable ref object that we can use as a reference inside a component....

To focus an input when another element is clicked in React: Set a ref attribute on the input element. Set an onClick attribute on the other element. When the other element is clicked, focus the input, e.g. ref.current.focus() . import { useRef } from ...