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To set conditional initial values ​​for useState in React: Pass a function to the useState hook. Use a condition to determine the correct initial value for the state variable. The function will only be called on the initial render. import {useStat...

To set default values ​​for Input elements in React: Pass the default value as a parameter to the useState hook for controlled fields. Set the defaultValue property on uncontrolled input fields. import {useRef, useState} from react ; export defaul...

To fix the error Export useHistory was not found in react-router-dom , use the useNavigate hook instead, e.g. const navigate = useNavigate() . This hook returns a function that allows us to navigate programmatically. // ?️ import useNavigate...

Use the borderRadius CSS property to set the border radius style of elements in React, such as div style={{border: 1px solid red, borderRadius: 30px}} . If we need to set the style of a specific border, use the corresponding property, such as borderBo...

Set the displayName property on your component to fix the Component definition is missing display name error, e.g. App.displayName = MyApp; . Alternatively, disable the ESLint rule for the line with the following comment - // eslint-disable-next-line ...

React.js error Expected corresponding JSX closing tag appears when we forget to close a tag in the JSX code. To fix the error, use self-closing tags like input / and make sure the order of opening and closing tags in the JSX code is correct....

To type the useState hook as an array of objects in React, use the hook's generics, such as const [employees, setEmployees] = useState{salary: number; name: string}[]([]) . The state variable can be initialized to an empty array and only accepts point...

To handle onChange event on select element in React: Set onChange attribute on select element. Save the value of selected option in state variable. Every time user changes the selected option, update the state variable. import {useState} from react...

Generate option tags for select from array in React: Iterate the array using map() method. In each iteration, return an option element. Pass a unique key attribute to each option element. const App = () = { const arr = [ { value...

To modify the value of a text area using onChange in React: Add an onChange property to the text area, setting it to a function. Store the value of the text area in the state via the useState hook. Update the state every time the user types in the tex...

To call a child function from a parent component in React: Wrap the Child component in forwardRef. Use the useImperativeHandle hook in child to add a function to Child. Use ref to call the Child function from Parent, e.g. childRef.current....

Use the addEventListener method in React's functional components: Set the ref attribute on the element. Use the current attribute on the ref to access the element. Add the event listener in the useEffect hook. import {useRef, useEffect} from react ; c...

The react-hooks/exhaustive-deps rule warns us when dependencies are missing in effect hooks. To get rid of the warning, move the function or variable declaration inside the useEffect hook, remember arrays and objects that change on each render, or dis...

To set a background image with inline styles in React: Set the style attribute on the img element. Set the backgroundColor property in the style object. For example, backgroundImage: url(${MyBackgroundImage}) . // ?️ import the image import M...

Passing data from child to parent in React: Pass a function as a prop to the Child component. Call the function in the Child component and pass the data as an argument. Access the data in the Parent function. import {useState} from react ; funct...