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Memory

 import React, { useState, useCallback } from 'react'; function ParentComponent() {   const [clickCount, setClickCount] = useState(0); // Changes on every button click   const [otherValue, setOtherValue] = useState(0); // Changes only when its button is clicked   // This function will always be recreated because 'clickCount' changes on every click   const incrementClickCount = useCallback(() => {     console.log('incrementClickCount called. Current clickCount:', clickCount);     setClickCount(prevCount => prevCount + 1);   }, [clickCount]); // Dependency: clickCount   // This function will only be recreated if 'otherValue' changes   // It demonstrates how useCallback *prevents* recreation when 'clickCount' changes   const updateOtherValue = useCallback(() => {     console.log('updateOtherValue called. Current otherValue:', otherValue);     setOtherValue(prevValue => prevValue + 1);   },...
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Usecallback 3

 The text in the image describes the useCallback hook in React: useCallback The useCallback hook is used to memoize functions in functional components. Its main purpose is to prevent the unnecessary re-creation of functions on every render of a component. By wrapping a function with useCallback, React caches the function instance and only returns a new instance if one of its specified dependencies has changed. import React, { useState, useCallback } from 'react'; function App() {   const [count, setCount] = useState(0);   // Function that is recreated on every render   const incrementWithoutCallback = () => {     setCount(count + 1);   };   // Function that is memoized; only recreated if 'count' changes   const incrementWithCallback =  useCallback(() => {     setCount(prevCount => prevCount + 1);   }, [count]);   return (     <div>       <p>Count: {count}</p> ...
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UseRef 2

 UseRef:- The useRef hook is primarily used for accessing and interacting with DOM elements. The advantage of the useRef hook is that it remains consistent across renders and doesn't trigger re-renders when its value changes import React, { useRef } from 'react'; function MyComponent() {   const inputRef = useRef(null);   const focusInput = () => {     if (inputRef.current) {       inputRef.current.focus();     }   };   return (     <div>       <h2>Using useRef Example</h2>       <input type="text" ref={inputRef} placeholder="Type something..." />       <button onClick={focusInput}>Focus Input</button>     </div>   ); } export d efault MyComponent;
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Lifecycle hooks and useEffect-1

 Here's the corrected document: Lifecycle Methods: When we perform tasks like:  * Component loads  * Component updates  * Component unmounts Class-based Components: We have:  * componentDidMount  * componentDidUpdate  * componentWillUnmount Functional-based Components: We use the useEffect hook. We need to pass dependencies:  * If passing an empty dependency array ([]), it will work as componentDidMount.  * If passing dependencies, it works as componentDidUpdate.  * If we pass a return keyword, it works as componentWillUnmount. Definition of useEffect: useEffect is React's solution for handling side effects in functional components. It allows your component to perform actions that go beyond just rendering UI. This means that the primary job of a React component is to display something on the screen. What are Side Effects? Actions that go beyond just rendering UI are called side effects. Examples of Side Effects:  * Fetching data fro...
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react element update in main

What is element in reactjs In React.js, an element is the smallest building block of a user interface (UI). It is a plain JavaScript object that describes a DOM node or a component instance. React elements are immutable, meaning that once they are created, they cannot be changed. Here's a breakdown of what you need to know about React elements: Key Concepts: * Representation of DOM nodes: React elements are not actual DOM elements. Instead, they are lightweight descriptions of what you want to see on the screen in terms of DOM nodes (like , , , etc.) or other components. * Immutability: React elements are immutable. Once you create an element, you cannot change its properties or children. This immutability helps React optimize rendering and improve performance. * Creation: You can create React elements using: * JSX: A syntax extension that looks like HTML but gets transformed into JavaScript function calls to create elements. * React.createElement(): The underlying functio...
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JS rawat

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Chapters-Covered Q1: what is javascript? What is the role of javascript engine? Q2: what are client side and server side? Q3: what are variables? What is the difference between var,let and const? Q4: what are some important string operations in js? Q5: What is DOM? What is the difference between HTML and DOM? Q6: What are selectors in JS? ers Q7: What is the difference between getElementById,getElementByClassName and getElementByTagName? Q8: What are data types in JS? Q9: What are operations? What are the types of operators in JS? Q10: What are the types of conditions statements in JS? Q11: What is loop? What are the types of loops in JS? Q12: What are Functions in JS? What are the types of function? Q13: What are Arrow Functions in JS? What is it use? Q14: What are Arrays in JS? How to get, add & remove elements from arrays? ...
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