Science Knowings: JavaScript Course For Social Media

Error Handling in Promises

Error Handling in Promises

Previously, we covered Promise Chaining, a powerful technique for sequencing asynchronous operations. Now, let's focus on Error Handling in Promises, a crucial aspect for building robust and reliable code.

Why Error Handling is Important

Error handling allows us to anticipate and respond to unexpected errors that may occur during asynchronous operations. By handling errors gracefully, we can prevent our applications from crashing and provide a better user experience.

Catching Errors with .catch()

The .catch() method enables us to handle errors that occur in a promise. It takes an error handling function as an argument, which receives the error object and can perform necessary actions.

Chaining .catch() for Multiple Error Handling

We can chain multiple .catch() handlers to handle different types of errors or perform specific actions for each error type. This allows for more granular error handling.

Using finally() to Execute Code Regardless of Errors

The .finally() method provides a way to execute code regardless of whether a promise resolves or rejects. This is useful for cleanup operations or logging purposes.

Promise.all() with Error Handling

Promise.all() processes multiple promises concurrently and returns a single promise. It rejects if any of the input promises reject, so proper error handling is crucial to prevent errors from propagating.

Promise.race() with Error Handling

Promise.race() returns the first promise that settles, regardless of whether it resolves or rejects. Error handling in Promise.race() requires handling the rejected promise to prevent uncaught errors.

Custom Error Objects

We can create our own custom error objects to provide more meaningful error messages and additional information about the error that occurred.

Throwing Custom Errors

Using throw keyword, we can throw custom errors to explicitly indicate an error condition and provide diagnostic information.

Error Handling in Async Functions

Async functions use try...catch blocks to handle errors. The try block contains the asynchronous code, while the catch block handles any errors that occur.

try...catch Blocks in Async Functions

try...catch blocks allow us to handle errors in asynchronous operations within async functions, providing a concise and readable way to handle errors.

Error Boundaries in React for UI Error Handling

React provides error boundaries to handle errors in React components. Error boundaries catch errors and display a fallback UI to prevent the application from crashing.

Best Practices for Error Handling in Promises

Best practices include using .catch() for error handling, chaining .catch() handlers, leveraging .finally() for cleanup, handling errors in Promise.all() and Promise.race(), and creating custom error objects.

Common Error Types in Promises

Common error types in Promises include network errors, syntax errors, and custom errors. It's important to anticipate and handle these error types gracefully.

Debugging Promises and Errors

Debugging Promises and errors involves using tools like console.log(), using breakpoints, and analyzing error messages to identify and resolve issues.

Next Topic: Async Functions in Classes

In the next session, we'll dive into Async Functions in Classes, a powerful feature that allows us to write asynchronous code in a cleaner and more organized way. Follow us to continue learning!