Asynchronous JavaScript : Callbacks, Promises, and Async/Await

function fetchData(callback) {
  setTimeout(() => {
    const data = "Data fetched successfully!";
    callback(data);
  }, 2000); // Simulate a 2-second network request
}

function processData(data) {
  console.log("Processing: " + data);
}

fetchData(processData);
console.log("Fetching data...");
// Expected Output:
// Fetching data...
// (after 2 seconds) Processing: Data fetched successfully!

function fetchData(callback) {
  setTimeout(() => {
    const data = "Data fetched successfully!";
    callback(data);
  }, 2000); // Simulate a 2-second network request
}

function processData(data) {
  console.log("Processing: " + data);
}

fetchData(processData);
console.log("Fetching data...");
// Expected Output:
// Fetching data...
// (after 2 seconds) Processing: Data fetched successfully!

// Example of Callback Hell
getData(function(a) {
  getMoreData(a, function(b) {
    getEvenMoreData(b, function(c) {
      getFinalData(c, function(d) {
        console.log(d);
      });
    });
  });
});

// Example of Callback Hell
getData(function(a) {
  getMoreData(a, function(b) {
    getEvenMoreData(b, function(c) {
      getFinalData(c, function(d) {
        console.log(d);
      });
    });
  });
});

function fetchDataPromise() {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      const success = true; // Simulate success or failure
      if (success) {
        resolve("Data fetched successfully with Promise!");
      } else {
        reject("Failed to fetch data with Promise.");
      }
    }, 2000);
  });
}

fetchDataPromise()
  .then(data => {
    console.log("Processing: " + data);
  })
  .catch(error => {
    console.error("Error: " + error);
  });

console.log("Fetching data with Promise...");
// Expected Output:
// Fetching data with Promise...
// (after 2 seconds) Processing: Data fetched successfully with Promise!

function fetchDataPromise() {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      const success = true; // Simulate success or failure
      if (success) {
        resolve("Data fetched successfully with Promise!");
      } else {
        reject("Failed to fetch data with Promise.");
      }
    }, 2000);
  });
}

fetchDataPromise()
  .then(data => {
    console.log("Processing: " + data);
  })
  .catch(error => {
    console.error("Error: " + error);
  });

console.log("Fetching data with Promise...");
// Expected Output:
// Fetching data with Promise...
// (after 2 seconds) Processing: Data fetched successfully with Promise!

fetchDataPromise()
  .then(data => {
    console.log(data); // "Data fetched successfully with Promise!"
    return "Further processing of " + data;
  })
  .then(processedData => {
    console.log(processedData);
    return "Final result: " + processedData;
  })
  .then(finalResult => {
    console.log(finalResult);
  })
  .catch(error => {
    console.error("Caught an error in the chain: " + error);
  });

fetchDataPromise()
  .then(data => {
    console.log(data); // "Data fetched successfully with Promise!"
    return "Further processing of " + data;
  })
  .then(processedData => {
    console.log(processedData);
    return "Final result: " + processedData;
  })
  .then(finalResult => {
    console.log(finalResult);
  })
  .catch(error => {
    console.error("Caught an error in the chain: " + error);
  });

async function getAndProcessDataWithError() {
  try {
    console.log("Attempting to fetch data...");
    const data = await new Promise((resolve, reject) => {
      setTimeout(() => {
        reject("Network error!"); // Simulate an error
      }, 1500);
    });
    console.log("Processing: " + data);
  } catch (error) {
    console.error("Caught error in async function: " + error);
  }
}

getAndProcessDataWithError();
// Expected Output:
// Attempting to fetch data...
// (after 1.5 seconds) Caught error in async function: Network error!

async function getAndProcessDataWithError() {
  try {
    console.log("Attempting to fetch data...");
    const data = await new Promise((resolve, reject) => {
      setTimeout(() => {
        reject("Network error!"); // Simulate an error
      }, 1500);
    });
    console.log("Processing: " + data);
  } catch (error) {
    console.error("Caught error in async function: " + error);
  }
}

getAndProcessDataWithError();
// Expected Output:
// Attempting to fetch data...
// (after 1.5 seconds) Caught error in async function: Network error!

function fetchDataAsync() {
  return new Promise((resolve) => {
    setTimeout(() => {
      resolve("Data fetched successfully with Async/Await!");
    }, 2000);
  });
}

async function getAndProcessData() {
  try {
    console.log("Fetching data with Async/Await...");
    const data = await fetchDataAsync(); // Pause execution until Promise resolves
    console.log("Processing: " + data);
  } catch (error) {
    console.error("Error: " + error);
  }
}

getAndProcessData();
// Expected Output:
// Fetching data with Async/Await...
// (after 2 seconds) Processing: Data fetched successfully with Async/Await!

function fetchDataAsync() {
  return new Promise((resolve) => {
    setTimeout(() => {
      resolve("Data fetched successfully with Async/Await!");
    }, 2000);
  });
}

async function getAndProcessData() {
  try {
    console.log("Fetching data with Async/Await...");
    const data = await fetchDataAsync(); // Pause execution until Promise resolves
    console.log("Processing: " + data);
  } catch (error) {
    console.error("Error: " + error);
  }
}

getAndProcessData();
// Expected Output:
// Fetching data with Async/Await...
// (after 2 seconds) Processing: Data fetched successfully with Async/Await!