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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...

Use the useSearchParams hook to programmatically update query parameters in React Router, for example, setSearchParams({query: myValue}) . The useSearchParams hook is used to read and modify the query string in the URL of the current location. import ...

To fix the React.js warning Invalid DOM property for . Did you mean tmlFor . Use the htmlFor attribute because for is a reserved word in JavaScript. Here is an example of how the warning is generated. export default function App () { // ⛔️ Warning...

React.js error X is not defined react/jsx-no-undef occurs when we forget to import a function, class, or variable before using it in our code. To fix this error, make sure to import the value before using it in our code, e.g. import {myFunc} from my-...

To set background color using inline styles in React: Set the style attribute on the element. Set the backgroundColor attribute to a specific color. import {useState} from react ; export default function App () { const [isActive, setIsActive] =...

To detect when the user presses the backspace key in React.js: Add the onKeyDown prop to the input element. Every time the user presses a key in the input field, check if the key pressed was the backspace key. Call a function or run some logic if it i...

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 Having an outdated ver...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...