Yes, if you want to run an async function after the page is loaded, you can put it inside a useEffect hook with an empty dependency array. This way, the function will only run once, right after the initial render of the component. Here's an example in JavaScript:

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useEffect(() => {
  // Define your async function
  const fetchData = async () => {
    // Perform async operations here
  };

  // Call the async function
  fetchData();
}, []);

By passing an empty dependency array ([]), you ensure that the useEffect hook is only executed once, similar to the "componentDidMount" lifecycle method in class components.

In React's useEffect hook, dependencies are used to control when the effect should run. If any of the dependencies specified in the dependency array change, the effect is re-evaluated. If none of the dependencies change, the effect is skipped.

Here's an example:

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import React, { useState, useEffect } from 'react';

function ExampleComponent() {
  const [count, setCount] = useState(0);

  useEffect(() => {
    // This effect will run whenever the 'count' state changes
    console.log("Count has changed!");
  }, [count]);

  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={() => setCount(count + 1)}>Increment</button>
    </div>
  );
}

In this example, the effect will only run when the count state changes. If count remains the same, the effect will be skipped. This allows you to control when certain actions or side effects should occur in your component.

To use the useEffect hook in React.js, you need to first import it from the react package.

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import React, { useEffect } from 'react';

The useEffect hook allows you to perform side effects in your functional components. It takes two parameters: a callback function and an optional array of dependencies.

The callback function will be called every time the component renders or re-renders. It is where you can place code that has side effects, such as fetching data from an API, subscribing to events, or manipulating the DOM.

Here's an example of using the useEffect hook to fetch data from an API when the component mounts:

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import React, { useEffect, useState } from 'react';

function MyComponent() {
  const [data, setData] = useState(null);

  useEffect(() => {
    fetch('https://api.example.com/data')
      .then(response => response.json())
      .then(data => setData(data))
      .catch(error => console.error(error));
  }, []);

  return (
    <div>
      {/* Render the fetched data */}
      {data ? (
        <ul>
          {data.map(item => (
            <li key={item.id}>{item.name}</li>
          ))}
        </ul>
      ) : (
        <p>Loading...</p>
      )}
    </div>
  );
}

In this example, the useEffect hook is called when the component mounts (since the dependency array is empty, []). It fetches data from an API and updates the data state using the setData function.

Remember to clean up any resources or subscriptions created within the useEffect callback by returning a cleanup function. This function will be called when the component is unmounted or before the next useEffect callback is called.

I hope this helps! Let me know if you have any further questions.

useState and useEffect are both hooks used in React, a JavaScript library for building user interfaces.

useState is a hook that allows you to add state to a functional component. State is a way of storing and managing data within a component. With useState, you can declare a state variable and a function to update that variable. Every time the state variable is updated, React will re-render the component and update the UI.

Here's an example of useState:

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import React, { useState } from 'react';

function Counter() {
  const [count, setCount] = useState(0);

  const incrementCount = () => {
    setCount(count + 1);
  };

  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={incrementCount}>Increment</button>
    </div>
  );
}

In the above example, we declare a state variable count and a function setCount to update it. Every time the "Increment" button is clicked, the incrementCount function is called and updates the count state variable. The component then re-renders and the updated count value is displayed.

useEffect is a hook used for side effects in React. Side effects are actions that happen outside of the normal flow of the component, such as fetching data, subscriptions, or manually manipulating the DOM. useEffect allows you to perform these side effects after the component has rendered.

Here's an example of useEffect:

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import React, { useState, useEffect } from 'react';

function Example() {
  const [count, setCount] = useState(0);

  useEffect(() => {
    document.title = `Count: ${count}`;
  }, [count]);

  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={() => setCount(count + 1)}>Increment</button>
    </div>
  );
}

In the above example, we use useEffect to update the document title based on the count state variable. The effect runs every time count changes. So, whenever the count is incremented, the document title will be updated to reflect the current count.

In summary, useState is used to manage state within a component, allowing you to store and update data. useEffect is used to perform side effects in a component, such as updating the document title, fetching data, or subscribing to events.

In React, the useEffect hook is used to perform side effects in functional components. The dependency array is an optional second argument that you can pass to the useEffect hook.

The dependency array defines dependencies for the effect. It specifies which values or variables inside the component should be watched for changes. When any of the dependencies change, the effect will be re-executed.

If the dependency array is empty, the effect will only run once after the initial render. If the dependency array is not provided, the effect will run after every render.

Here is an example of how to use the dependency array in the useEffect hook:

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import { useEffect, useState } from 'react';

function MyComponent() {
  const [count, setCount] = useState(0);

  useEffect(() => {
    // This effect will only run when 'count' changes
    console.log('The count has changed:', count);
  }, [count]);

  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={() => setCount(count + 1)}>Increment</button>
    </div>
  );
}

In the example above, the effect will only run when the value of the count state variable changes. If the count value is updated by clicking the "Increment" button, the effect will run again.

This can be useful when you want to perform certain actions whenever specific values in your component change. It helps to optimize performance and prevent unnecessary re-rendering of components.

To refactor the given jQuery code in React, you can use Refs along with JSX to achieve the same functionality. Here's an example:

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import React, { useRef, useEffect } from 'react';

const MyComponent = () => {
  const tabPaneRef = useRef(null);

  useEffect(() => {
    if (tabPaneRef.current) {
      const elements = tabPaneRef.current.querySelectorAll('.carousel-inner, .carousel-control, .close, .carousel-indicators-cell');
      for (let i = 0; i < elements.length; i++) {
        elements[i].style.display = '';
      }
    }
  }, []);

  return (
    <div className="tab-pane active" ref={tabPaneRef}>
      {/* Rest of your component */}
    </div>
  );
};

export default MyComponent;

In this refactored code, we use the useRef hook to create a reference to the tab pane element. With the help of the useEffect hook, we can run the code to select the desired elements and update their display property to an empty string.

Please note that the specific implementation may vary depending on your application's structure and requirements.

useEffect and useCallback are both React hooks used for different purposes.

useEffect is used to perform side effects, such as fetching data from an API, updating the DOM, or subscribing to an event listener, after a component renders or updates. It takes two parameters: a function containing the side effect logic and an array of dependencies used to determine if that effect needs to be re-executed.

Here's an example in JavaScript:

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import React, { useState, useEffect } from 'react';

function MyComponent() {
  const [count, setCount] = useState(0);

  useEffect(() => {
    document.title = `Count: ${count}`;
  }, [count]);

  const handleClick = () => setCount(count + 1);

  return (
    <div>
      <p>Count: {count}</p>
      <button onClick={handleClick}>Increment</button>
    </div>
  );
}

In this example, the useEffect hook updates the document title with the current count value whenever it changes.

useCallback is used to memoize a function, meaning it caches it so it doesn't get recreated on every render. This helps optimize performance, especially in cases where the function is passed as a prop to a child component. It takes two parameters: the function to memoize and an array of dependencies on which it depends.

Here's an example in JavaScript:

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import React, { useState, useCallback } from 'react';

function MyComponent() {
  const [count, setCount] = useState(0);

  const handleIncrement = useCallback(() => {
    setCount(prevCount => prevCount + 1);
  }, []);

  return (
    <div>
      <p>Count: {count}</p>
      <ChildComponent onIncrement={handleIncrement} />
    </div>
  );
}

function ChildComponent({ onIncrement }) {
  return (
    <div>
      <button onClick={onIncrement}>Increment</button>
    </div>
  );
}

In this example, the handleIncrement function is memoized using the useCallback hook so it doesn't get recreated on every render. It's then passed down as a prop to the ChildComponent component where it's used as an event handler for a button click.

This block of code is a custom React hook called useUniversalEffect. It has two parameters, effect and dependencies which are callbacks that get executed inside the hook.

The first import in the code is useEffect from the "react" package which is used to update state based on some condition. The next import is useNavigate from "react-router-dom" package, which is a hook that provides a way to navigate declaratively to any location in the application defined by the props of the component.

The function useUpdateEffect is a custom React hook that is used within the useUniversalEffect hook. It's used to run an effect on component updates, but not on initial render. This custom hook takes two parameters: effect and dependencies, where effect is the effect that needs to be run and dependencies is an array of values that the hook needs to monitor. If dependencies are not provided, the hook default to an empty array.

Within the useUpdateEffect function, the React.useRef() method is used to set the isFirstRender variable as a true boolean value for the first time and it is not updated unless the component re-renders. When the component re-renders, the useEffect function is triggered. If it's the first render of the component, the value of the isFirstRender is set to false. If it's not the first render, it will return the effect

Finally, the useUniversalEffect function definition is using the useUpdateEffect function, and it takes two parameters: effect and dependencies. effect is the effect that needs to be run while dependencies is an array containing all the dependencies required for the defined effect. The navigate method provided by the useNavigate hook and dependencies are included in the array of dependencies.

This custom hook useUniversalEffect will execute the effect on initial render as well as on every dependency list for any location change made by the user.

useEffect and useState are both hooks in React that allow us to manage state and side-effects in our functional components.

useState is used to declare a state variable and also a method to update its value. It takes an initial value as an argument and returns an array with two elements: the current state value and a function to update it.

Here's an example:

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import React, { useState } from "react";

function Example() {
  const [count, setCount] = useState(0);

  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>Click me</button>
    </div>
  );
}

useEffect is used to manage side-effects in our components, such as fetching data or manually updating the DOM. It runs after every render of a component, and takes two arguments: a function to run after rendering and an array of dependencies. The function will be ran whenever one of the dependencies changes, or if the dependency array is empty, it will only run once.

Here's an example:

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import React, { useState, useEffect } from "react";

function Example() {
  const [count, setCount] = useState(0);

  useEffect(() => {
    document.title = `You clicked ${count} times`;
  }, [count]);

  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>Click me</button>
    </div>
  );
}

In short, useState is used to manage state within a component, while useEffect is used to manage side-effects and runs after each render of a component.

Sure, here's a simple explanation and example of useEffect and fetch in React:

useEffect is a hook in React that allows us to run side effects or manage state changes after the component has rendered and the DOM has been updated. This means that we can use useEffect to fetch data from an API, update the state, and re-render the component with the new data.

fetch is a built-in function in JavaScript that allows us to make HTTP requests to a server. We can use fetch to retrieve data from an API endpoint and then use that data in our React component.

Here's an example:

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import React, { useState, useEffect } from 'react';

function App() {
  const [data, setData] = useState([]);

  useEffect(() => {
    const fetchData = async () => {
      const response = await fetch('https://jsonplaceholder.typicode.com/users');
      const jsonData = await response.json();
      setData(jsonData);
    }
    fetchData();
  }, []);

  return (
    <div>
      <h1>List of Users</h1>
      <ul>
        {data.map(user => (
          <li key={user.id}>
            {user.name} ({user.email})
          </li>
        ))}
      </ul>
    </div>
  );
}

export default App;

In this example, we are making an HTTP request to the JSONPlaceholder API using fetch. We then use useState to create a state variable called data and initialize it to an empty array. In useEffect, we define a function called fetchData that makes an API request using fetch, parses the response using response.json(), and then updates the state using setData. We then call fetchData inside useEffect to fetch the data when the component first renders (since we pass an empty dependency array as the second argument to useEffect). Finally, we map over the data array and display each user's name and email in an unordered list.

I hope that helps! Let me know if you have any more questions.

useEffect is a hook in the React library that allows developers to manage side effects in their components. Side effects include anything that affects something outside of the scope of the component such as manipulating the DOM, fetching data from an API, or setting up event listeners. It takes in a function as its first argument and an array as its second argument. The function is invoked after every render, except for the first render. The array is used to optimize the hook and determine when to re-run the function. If the array is empty, the function only runs once. You can learn more about the useEffect hook in the official React documentation: https://reactjs.org/docs/hooks-effect.html

useEffect is a built-in hook in React that allows you to perform side effects in your functional component. A side effect is anything that affects something outside of your component, like fetching data from an API, updating the document's title, subscribing to a WebSocket, etc. useEffect takes two parameters: a function (the effect), and an array of dependencies (optional). The function will run every time the component renders, unless the dependencies don't change since the last render. The second parameter is an array of values that your effect needs to use. If any of the values change, the effect will run again with the updated values. Here's an example of useEffect in action:

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import { useState, useEffect } from 'react';

function Example() {
  const [count, setCount] = useState(0);

  useEffect(() => {
    document.title = `You clicked ${count} times`;
  }, [count]);

  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>Click me</button>
    </div>
  );
}

In this example, the effect sets the document's title to reflect the current count value. The effect only runs again if the count value changes.

Here's an example code in React.js to get the API from Spotify and show "Sweet Child O' Mine" by Guns N' Roses. Please note that you need to have a Spotify Developer Account to get your own Client ID and Client Secret.

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import React, { useEffect, useState } from "react";

const App = () => {
  const accessToken = ""; //Replace with your Access Token obtained from Spotify API
  const [songData, setSongData] = useState(null);

  useEffect(() => {
    fetch(
      "https://api.spotify.com/v1/search?q=sweet%20child%20o%20mine%20artist:guns%20n%20roses&type=track&limit=1",
      {
        headers: {
          Authorization: `Bearer ${accessToken}`,
        },
      }
    )
      .then((response) => response.json())
      .then((data) => setSongData(data.tracks.items[0]));
  }, []);

  return (
    <div>
      {songData ? (
        <div>
          <h1>{songData.name}</h1>
          <p>{songData.artists[0].name}</p>
          <img src={songData.album.images[0].url} alt="Album Cover" />
        </div>
      ) : (
        <p>Loading...</p>
      )}
    </div>
  );
};

export default App;

Explanation of the code:

• Import React, useState, and useEffect hooks from "react" library.
• Create a functional component named "App".
• Declare and initialize "accessToken" to your own Access Token obtained from Spotify API.
• Declare "songData" state variable and initialize it to "null".
• Use useEffect hook to fetch data from Spotify API. In this example, we will search for "Sweet Child O' Mine" by "Guns N' Roses" using the keyword query parameter "q" and the artist parameter "artist". The search is limited to one track only to simplify the code. Once the data is fetched, we set the "songData" state to the first item of the fetched tracks array.
• Return a div that displays the data using JSX by checking if "songData" is truthy or falsy. If "songData" is truthy, display the song name, artist name, and album cover using "songData" properties. If "songData" is falsy, display "Loading..." instead.

Please note that the Access Token should be obtained from Spotify API explicitly, and you should not include secrets in the frontend code like shown in this example. Passing them as props from server-side is an example of a better way to do it from the security perspective.

To use another state to record when your application is loading data from the API, you can create a boolean isLoading state in your component. Whenever you initiate the API request, you can set isLoading to true, and when the API request finishes, you can set it to false.

You can display a loading message whenever the isLoading state is true using a conditional statement. Here's an example code snippet in React:

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import React, { useState, useEffect } from 'react';

function MyComponent() {
  const [isLoading, setIsLoading] = useState(false);
  const [data, setData] = useState([]);

  useEffect(() => {
    setIsLoading(true);
    fetch('https://api.example.com/data')
      .then(response => response.json())
      .then(data => {
        setData(data);
        setIsLoading(false);
      });
  }, []);

  return (
    <div>
      {isLoading ? <p>Loading...</p> : null}
      {/* Render the fetched data here */}
    </div>
  );
}

In this example, we create a isLoading state using the useState hook and initialize it to false. In the useEffect hook, we initiate the API request and set isLoading to true before the fetch. Once the API request is complete, we set isLoading back to false.

In the return statement, we check if isLoading is true, and if so, we display a loading message. If isLoading is false, we continue to render the fetched data.

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import React, { useState, useEffect } from "react";
import axios from "axios";

const App = () => {
  const [data, setData] = useState([]);

  useEffect(() => {
    const fetchData = async () => {
      const result = await axios("your_external_data_url");
      setData(result.data);
    };
    fetchData();
  }, []);

  return (
    <div>
      <h1>Data from External Source:</h1>
      <ul>
        {data.map((item) => (
          <li key={item.id}>{item.name}</li>
        ))}
      </ul>
    </div>
  );
};

export default App;

Note:

• Make sure to replace "your_external_data_url" with the actual URL to your external data source.
• Also, you can modify the code inside the fetchData arrow function based on the structure of your external data source.
• Finally, make sure to install axios by running npm install axios in your terminal before using it in your React project.

In React, you can use the addEventListener method inside a component by using a ref. Here's an example in JavaScript:

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import React, { useRef, useEffect } from 'react';

function MyComponent() {
  const myRef = useRef(null);

  useEffect(() => {
    myRef.current.addEventListener('click', handleClick);
    return () => {
      myRef.current.removeEventListener('click', handleClick);
    };
  }, []);

  const handleClick = (event) => {
    console.log('Clicked!');
  };

  return <button ref={myRef}>Click me</button>;
}

In this example, we use the useRef hook to create a ref and attach it to the button element using the ref prop. The useEffect hook is used to add an event listener to the button element on mount, and remove it on unmount. When the button is clicked, the handleClick function is called and logs "Clicked!" to the console. This is just one example, and addEventListener can be used with other events and elements as well.

To detect whether the user is accessing the app via a Mac or Windows system, you can check for the navigator.platform property. This property contains information about the operating system of the client.

Here's an example of how to do it in JavaScript:

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const isMac = navigator.platform.toUpperCase().indexOf('MAC') >= 0;

if (isMac) {
  // display cmd+enter shortcut
} else {
  // display ctrl+enter shortcut
}

You can then display the appropriate shortcut based on the result of the check.

To add a listener to trigger the form's submission when the user presses the shortcut, you can use the addEventListener method on the document object to listen for a keydown event. The keydown event provides information about which key was pressed.

Here's an example of how to do it in JavaScript:

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const form = document.getElementById('myForm');

document.addEventListener('keydown', (event) => {
  if ((isMac && event.metaKey && event.keyCode === 13) ||
      (!isMac && event.ctrlKey && event.keyCode === 13)) {
    form.submit();
  }
});

This code listens for the keydown event on the document, and when it detects the appropriate shortcut (cmd+enter for Mac or ctrl+enter for Windows), it submits the form. Note that event.metaKey is used for Mac and event.ctrlKey is used for Windows to check whether the command or control key was pressed. The keyCode property contains the code for the key that was pressed, and 13 is the code for the Enter key.

Here's an example of how it can be used in ReactJS:

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import React, { useEffect } from 'react';

function MyForm() {
  const isMac = navigator.platform.toUpperCase().indexOf('MAC') >= 0;

  useEffect(() => {
    const form = document.getElementById('myForm');

    const handleKeyDown = (event) => {
      if ((isMac && event.metaKey && event.keyCode === 13) ||
          (!isMac && event.ctrlKey && event.keyCode === 13)) {
        form.submit();
      }
    };

    document.addEventListener('keydown', handleKeyDown);

    return () => {
      document.removeEventListener('keydown', handleKeyDown);
    };
  }, [isMac]);

  return (
    <form id="myForm">
      {/* form fields and submit button here */}
    </form>
  );
}

In this example, the useEffect hook is used to add and remove the keydown event listener, and the isMac variable is passed as a dependency to the hook so that it will update if the user switches between Mac and Windows during the session.

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import React, { useState, useEffect } from "react";
import data from "./data.json";

function App() {
  const [items, setItems] = useState([]);

  useEffect(() => {
    setItems(data);
  }, []);

  const deleteItem = (id) => {
    const newItems = items.filter((item) => item.id !== id);
    setItems(newItems);
  };

  return (
    <div>
      {items.map((item) => (
        <div key={item.id}>
          <h3>{item.name}</h3>
          <button onClick={() => deleteItem(item.id)}>Delete</button>
        </div>
      ))}
    </div>
  );
}

export default App;

Explanation:

• We import our JSON data at the top of the file using import data from "./data.json".
• We create a state variable items to store our data and to be able to modify it using the useState hook.
• We use the useEffect hook to set the items state to our data as soon as the component is mounted.
• We define the deleteItem function to remove an item from the items state array by filtering it out based on the id of the item.
• We map over our items state array to display each item along with a "Delete" button that triggers the deleteItem function when clicked.

Note: Make sure to replace data.json with the correct file path to your JSON file.

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import React, { useState, useEffect } from "react";

function App() {
  const [showButton, setShowButton] = useState(true);

  useEffect(() => {
    const handleResize = () => {
      if (window.innerWidth < 768) {
        setShowButton(false);
      } else {
        setShowButton(true);
      }
    };

    window.addEventListener("resize", handleResize);
    return () => window.removeEventListener("resize", handleResize);
  }, []);

  return (
    <div>
      {showButton && <button>Click me!</button>}
    </div>
  );
}

This code snippet uses the useState hook to create a boolean state variable showButton which controls whether or not the button is displayed.

The useEffect hook is used to add a listener for the resize event on the window object. Whenever the window is resized, the handleResize function is called which checks the window width and sets the showButton state accordingly.

The return function inside the useEffect hook is used to remove the event listener when the component unmounts, and prevent memory leaks.

Finally, the showButton state is used to conditionally render the button. The button is only displayed if showButton is true.

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<!-- HTML code -->
<div class="progress-container">
  <div class="progress-bar" style="width: 50%"></div>
  <div class="progress-value">50</div>
</div>
<button id="minus-button">-</button>
<button id="plus-button">+</button>

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/* CSS code */
.progress-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  margin: 20px;
}
.progress-bar {
  width: 0%;
  height: 20px;
  margin-bottom: 10px;
  background-color: blue;
}
.progress-value {
  font-size: 18px;
}
button {
  font-size: 18px;
  padding: 10px;
  margin: 5px;
  border: none;
  border-radius: 5px;
  background-color: lightgray;
}
button:disabled {
  background-color: gray;
}

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// JavaScript code using React hooks
import React, { useState, useEffect } from 'react';

const ProgressBar = ({ value }) => {
  const [progress, setProgress] = useState(0);

  useEffect(() => {
    setProgress(value > 100 ? 100 : value < 0 ? 0 : value);
  }, [value]);

  const handleMinusClick = () => {
    setProgress(prevProgress => {
      const newProgress = prevProgress - 1;
      return newProgress < 0 ? 0 : newProgress;
    });
  };

  const handlePlusClick = () => {
    setProgress(prevProgress => {
      const newProgress = prevProgress + 1;
      return newProgress > 100 ? 100 : newProgress;
    });
  };

  return (
    <div className="progress-container">
      <div className="progress-bar" style={{ width: `${progress}%` }} />
      <div className="progress-value">{progress}</div>
      <button
        id="minus-button"
        onClick={handleMinusClick}
        disabled={progress <= 0}
      >
        -
      </button>
      <button
        id="plus-button"
        onClick={handlePlusClick}
        disabled={progress >= 100}
      >
        +
      </button>
    </div>
  );
};

export default ProgressBar;

useEffect is a React Hook that lets you synchronize a component with the browser’s lifecycle events, so you can modify the component’s behavior or appearance as needed. You should use useEffect to perform actions that must be done synchronously with lifecycle changes, like setting up event listeners, fetching data or performing cleanups. You can learn more about useEffect on React's official documentation here: https://reactjs.org/docs/hooks-effect.html

Here's an example of using useEffect in JavaScript:

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import React, { useState, useEffect } from 'react';

function App() {
  const [data, setData] = useState(null);

  useEffect(() => {
    // Fetch data from an API when the component mounts
    fetch('https://api.example.com/data')
      .then(response => response.json())
      .then(data => setData(data));

    // Remove the event listener and clean up when the component unmounts
    return () => {
      document.removeEventListener('click', handleClick);
    }
  }, []);

  // Log the data to the console when it updates
  useEffect(() => {
    console.log(data);
  }, [data]);

  // Handle clicks on the document
  function handleClick() {
    console.log('Document clicked!');
  }

  return (
    <div>
      <h1>{data ? data.title : 'Loading...'}</h1>
    </div>
  );
}

export default App;

In this example, useEffect is used to fetch data from an API when the component mounts, log the data to the console when it updates, and remove an event listener and clean up when the component unmounts. The empty array [] as the second argument to useEffect indicates that we want to run the effect only once, when the component mounts, and not after every re-render. The data variable is included as a dependency array to the second useEffect so that it only logs the data when it updates.

React Hooks are functions that let you ‘hook into’ React features from function components. They are mainly used for state management inside components. Using hooks, you can use local state inside simple components, write custom hooks to reuse your stateful logic and also use React’s built-in hooks like useState and useEffect which allow you to set local state and access lifecycle features from functional components.

For example you can use the useState hook to create a local state variable and set its initial value like this:

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import React, { useState } from "react";

const Example = () => {
  const [count, setCount] = useState(0);

  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>
        Click me
      </button>
    </div>
  );
}

React also has two other built-in hooks, useEffect and useContext, as well as many transition and form hooks.

For more information, please see the official React documentation: https://reactjs.org/docs/hooks-intro.html

Hooks are a way to use state and other React features without writing a class. They let you use React features, such as useState and useEffect, in functional components. When you call a Hook like useState inside a component, React saves the value that it returns in the component’s state.

For example, the following component uses the useState Hook to store a count:

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import React, { useState } from 'react';

function Example() {
  // Declare a new state variable, which we'll call "count"
  const [count, setCount] = useState(0);

  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>
        Click me
      </button>
    </div>
  );
}

The useEffect hook is a way to "box" code inside a React component to run at certain times. React offers a few built-in methods to do this, and componentDidUpdate is one of them. To use componentDidUpdate with useEffect, the syntax would look like this:

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useEffect(() => {
  // Run after each render
  componentDidUpdate(prevProps, prevState) {
     // Do stuff
  }
}, [dependencies]);

dependencies is an array of values that will be checked to determine if the componentDidUpdate method should be run. When that array is omitted, the effect will run on every render. For more information, see this article from LogRocket.

In ReactJS, we can use the useEffect() hook to get real time changes of an API in components without any refresh of the page. useEffect() is a combination of componentDidMount, componentDidUpdate and componentWillUnmount lifecycle methods. It is an essential React hook that allows components to respond to the changes in state or props and produce a side effect accordingly.

To fetch data from an API and update a component, the useEffect() hook can be used in the following code example:

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import React, { useState, useEffect } from 'react';

function Example() {
  const [data, setData] = useState([]);

  useEffect(() => {
    async function fetchData() {
      const result = await fetch(`url-to-the-api`);
      const body = await result.json();
      setData(body);
    }
    fetchData();
  }, []);

  return <div>{data}</div>;
}

export default Example;

The useEffect() hook ensures that the API is called and the data is updated each time the component updates. This allows for real time changes without refreshing the page.

Reference: https://www.freecodecamp.org/news/how-to-fetch-data-from-an-api-with-react-hooks-237462/