Gain insights into JavaScript Promises to handle asynchronous events, chain multiple promises, utilize built-in methods, and master async functions with await expressions for efficient event handling.



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JS promises

promises

Promises are used to deal with event handling and callbacks in asynchronous programming in JavaScript, such as clicks and key presses. Promises allow developers to specify a function to execute at some later point in response to certain events. Promises may also indicate whether a certain code succeeded or failed in performing its assigned job.

In this course, you will learn how to chain different promises, which makes the code easier to understand and debug. Next, you’ll learn built-in methods to monitor and respond to multiple promises executing in parallel. Then, you will cover async functions and await expressions that are often used with promises. Finally, you’ll learn how to track promises when they are rejected without a rejection handler.

Promises are important to understand and debug the code in asynchronous programming. The concepts of JS promises help developers working with Node.js and Deno for event handling and with asynchronous JavaScript APIs.

JavaScript Promises

## Handling multiple promises
For times when we want to monitor and respond to multiple promises at the same time, JavaScript provides several methods. Each method behaves slightly differently, but they all allow us to run promises in parallel and respond to them as a group:
- `Promise.all()`: The returned promise is fulfilled when all of the promises are fulfilled, and the returned promise is rejected when any promise is rejected.
- `Promise.allSettled()`: The returned promise is always fulfilled with an array
of results from the promise, and the returned promise is never rejected.
- `Promise.any()`: The returned promise is fulfilled when the first promise is fulfilled, and the returned promise is rejected when all of the promises are
rejected.
- `Promise.race()`: The returned promise is fulfilled when the first promise to
settle is fulfilled, and the returned promise is rejected when the first promise to settle is rejected.

Each of these methods is appropriate for different use cases, and it’s up to you to decide which is appropriate in any given situation.

# Handling multiple promises
For times when we want to monitor and respond to multiple promises at the same time, JavaScript provides several methods. Each method behaves slightly differently, but they all allow us to run promises in parallel and respond to them as a group:
- `Promise.all()`: The returned promise is fulfilled when all of the promises are fulfilled, and the returned promise is rejected when any promise is rejected.
- `Promise.allSettled()`: The returned promise is always fulfilled with an array
of results from the promise, and the returned promise is never rejected.
- `Promise.any()`: The returned promise is fulfilled when the first promise is fulfilled, and the returned promise is rejected when all of the promises are
rejected.
- `Promise.race()`: The returned promise is fulfilled when the first promise to
settle is fulfilled, and the returned promise is rejected when the first promise to settle is rejected.

Each of these methods is appropriate for different use cases, and it’s up to you to decide which is appropriate in any given situation.

Get a brief summary of working with multiple promises.

Introduction

Basics of Promises

Chaining Promises

Working with Multiple Promises

Async Functions and Await Expressions

Tracking Down the Unhandled Rejections

Conclusion

Summary: Working with Multiple Promises

Handling multiple promises