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Home Forums How does error handling work in asynchronous JavaScript? – MindStick
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2 Answers

Gulshan Negi
Gulshan Negi 16 Oct 2023
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Well, error handling in asynchronous JavaScript involves dealing with errors that may occur during the execution of asynchronous code, such as when working with callbacks and promises. 
Code example:- 

function fetchDataFromServer(callback) {
 setTimeout(function() {
   const error = null; // Set to an error object to simulate an error
   if (error) {
     callback(error, null);
   } else {
     const data = "Data from server";
     callback(null, data);
   }
 }, 1000);
}
fetchDataFromServer(function(error, data) {
 if (error) {
   console.error("Error:", error);
 } else {
   console.log(data);
 }
});

Thanks

Aryan Kumar
Aryan Kumar 11 Oct 2023
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Error handling in asynchronous JavaScript involves handling errors that may occur in asynchronous operations such as Promises, async/await, or callback functions. Here's a simplified explanation of how it works with code examples:

Promises: Promises are a way to manage asynchronous operations and handle errors. You can use the .catch() method to handle errors in a clean and readable way.

async function fetchData() {
  return fetch('https://api.example.com/data')
    .then(response => {
      if (!response.ok) {
        throw new Error('Failed to fetch data');
      }
      return response.json();
    })
    .catch(error => {
      console.error('Error:', error.message);
    });
}

Async/Await: Async/await is a more modern way to write asynchronous code. You can use try...catch blocks to handle errors.

async function fetchData() {
  try {
    const response = await fetch('https://api.example.com/data');
    if (!response.ok) {
      throw new Error('Failed to fetch data');
    }
    const data = await response.json();
    return data;
  } catch (error) {
    console.error('Error:', error.message);
  }
}

Callbacks: In callback-based asynchronous code, you can pass an error as the first argument in the callback function to handle errors.

function fetchData(callback) {
  fetch('https://api.example.com/data', (error, response) => {
    if (error) {
      console.error('Error:', error.message);
      callback(error);
    } else {
      if (!response.ok) {
        callback(new Error('Failed to fetch data'));
      } else {
        response.json(data => {
          callback(null, data);
        });
      }
    }
  });
}

In all these examples, errors are detected and handled. When an error occurs, it's either logged or passed to a callback function, depending on the method used. This way, you can gracefully handle errors in asynchronous JavaScript without causing your code to crash.

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