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Use square bracket notation to set and access state in React using dynamic keys, for example, setEmployee({...employee, [key]: employee.salary + 100}) . The variable or expression in the square brackets will be evaluated before setting the state. impo...

To change the style of an element using ref in React: Set the ref attribute on the element. Access the element through the current attribute on the ref. Update the element's style, for example ref.current.style.backgroundColor = green . import { useRe...

To get the height of an element using ref in React: Initialize a state variable that will store the element's height. Update the element's height in the useEffect() hook. The height should be set to ref.current.clientHeight . import {useEffect, useSta...

To pass a boolean value as props to a component in React, wrap the boolean value in curly braces, e.g. Child bool={true} / . All non-string props that we pass to a component must be enclosed in curly braces. function Child ( {bo...

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...

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-...