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Use the useEffect hook to call a function only once in React. When the useEffect hook is passed an empty dependencies array, it runs only when the component mounts. This is the preferred approach when we have to fetch data when the component mounts....

To replace an object in an array in React state: Use the map() method to iterate over the array. In each iteration, check if a certain condition is met. Replace the objects that meet the condition and return all other objects as is....

To qualify the useState hook object in React, use the hook's generic type, for example, const [employee, setEmployee] = useState{name: string; salary: number}({name: ,salary: 0}) . The state variable will only accept key-value pairs of the specified t...

Use the textDecoration property to add a strikethrough to text in React, for example, span style={{textDecoration: line-through}} . The text-decoration CSS property sets the appearance of text decoration lines. const App = () = { return ( div h2 span ...

To go back to the previous page with React Router: Use the useNavigate() hook, e.g. const navigate = useNavigate(); . Calls the navigate() function passed to it -1 - navigate(-1) . Calling navigate with -1 is the same as clicking the back button. impo...

To open a file input on button click in React: Set the onClick attribute on the button element. Set the ref attribute on the file input. When the button is clicked, open the file input, e.g. inputRef.current.click() . App.js import { useRef } from...

To cross out text on click in React: Set an onClick attribute on the element. When the element is clicked, check if its text-decoration attribute is set. If the attribute is set, remove it, otherwise set it to line-through. const App =...

Use spread syntax to combine multiple inline style objects in React, for example style={{...style1, ...style2}} . The spread syntax will unpack the key-value pairs of the object into a final object and the styles will be applied to the element. export...

Generates the error Functions are not valid as a React child. This may happen if you return a Component instead of from render. There are 2 common reasons: Returning a function reference instead of a component from render. Using React Router routes as...

To find an object in an array in React: Call the find() method on the array and pass it a function. The function should return an equality check for the relevant properties. The find() method returns the first value in the array that satisfies the con...

To detect when the Esc key is pressed in React.js: Add a keydown event listener to the document element. When the user presses a key, check if the key is Esc. If the key pressed is Escape, call a function or run some logic. import {u...

To check if a browser tab has focus using React: Add event listeners for the focus and blur events. If the focus event is fired, the tab has focus. If the blur event is fired, the tab loses focus. import {useE...

To delete query parameters using React Router: Use the useSearchParams hook to get the search parameters for the current location. Use the delete() method to delete each query parameter, such as searchParams.delete('q'). To update the search parameter...

In React, we use the String() function to render boolean values ​​in JSX, for example, h2{string(bool1)}/h2 . By default, boolean values ​​don’t render anything in React, so we have to convert the value to a string in order to render it. exp...

To create an input field in React.js that only contains numbers: 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 { useState } from reactjs...