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

# Introduction
Promises may seem like little more than an incremental improvement over using some combination of a callback and the `setTimeout()` function, but there is much more to promises than meets the eye. More specifically, there are several ways to chain promises to accomplish more complex asynchronous behavior.

Each call to `then()`, `catch()`, or `finally()` actually creates and returns another promise. This second promise is settled only once the first has been fulfilled or rejected. Consider this example:

const promise = Promise.resolve(66);

promise.then(value => {
    console.log(value);
}).then(() => {
    console.log("Finished");
});

The call to `promise.then()` returns a second promise on which `then()` is called. The second `then()` fulfillment handler is called only after the first promise has been resolved. If we unchain this example, it looks like this:

Get started with chaining promises and catching errors.

Introduction

Basics of Promises

Chaining Promises

Working with Multiple Promises

Async Functions and Await Expressions

Tracking Down the Unhandled Rejections

Conclusion

Fundamentals of Chaining Promises

Introduction