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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 fix the issue of input fields not working in React, make sure to use the defaultValue property instead of the value of the uncontrolled input field. Alternatively, set an onChange property on the field and handle the change event. Here is an exampl...

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 ...

To set the height of a Div in React to cover the entire screen, set its height to 100vh, for example div style={{height: 100vh}}.../div . When the element's height is set to 100vh, it covers 100% of the viewport height. const App = () = { return...

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...