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React refs most often return undefined or null when we try to access their current properties before the corresponding DOM element is rendered. To fix this, you need to access the ref in the useEffect hook or when an event is triggered. import {useRef...

Unexpected default export of anonymous function warning is caused when we try to export an anonymous function using default export. To fix the error, name the function before exporting it. Below is a sample code Header.js that produces the above error...

When we use the useState hook to declare an empty state array but do not type the array, we get the error Type is not assignable to type never. To fix the error, use generics to type the state array, such as const [arr, setArr] = useStatestr...

To prevent a page refresh when a form is submitted in React, use the preventDefault() method on the event object, for example event.preventDefault() . The preventDefault() method prevents the browser from taking the default action, which in the case o...

The Nothing was returned from render React error occurs when we forget to explicitly return a value from a function or class component. To fix the error, explicitly return JSX from our component, use implicit returns with arrow functions, or...

To create N identical components/elements in React: Use Array.from() method to generate an array of N elements. Replace each element in the array with the actual component. Render the array of elements. function Header () { return h2 Hello world / h2 ...

React.jsAttempted import error X is not exported from appears when we try to import a named import that does not exist in the specified file. To resolve the error, make sure the module has named exports and that we are not mixing named exports with de...

To concatenate JSX elements into an array in React: Initialize an empty array. Use the push() method to push JSX elements into the array. Set the key attribute on the outermost JSX element to a unique value. export default function App () { const fru...

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 Having an outdated ver...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...