JavaScript promises helps us to handle asynchronous operations more efficiently by assigning the handler with the success value or failure reason.

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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

We want to use `Promise.all()` in any situation where we are waiting for multiple promises to fulfill and any one failure could cause the entire operation to fail. Here are some common use cases for `Promise.all()`.

## Processing multiple files together
When using a server-side JavaScript runtime, such as Node.js or Deno, we may need to read from multiple files to work with data contained inside. In this situation, it’s most efficient to read files in parallel and wait until they’ve all been read before proceeding to process the data we’ve retrieved. Here’s an example that works in Node.js:

We want to use `Promise.all()` in any situation where we are waiting for multiple promises to fulfill and any one failure could cause the entire operation to fail. Here are some common use cases for `Promise.all()`.

# Processing multiple files together
When using a server-side JavaScript runtime, such as Node.js or Deno, we may need to read from multiple files to work with data contained inside. In this situation, it’s most efficient to read files in parallel and wait until they’ve all been read before proceeding to process the data we’ve retrieved. Here’s an example that works in Node.js:

Learn how Promise.all() processes multiple files, calls multiple APIs, and creates artificial delays.

Introduction

Basics of Promises

Chaining Promises

Working with Multiple Promises

Async Functions and Await Expressions

Tracking Down the Unhandled Rejections

Conclusion

When to Use the Promise.all() Method

Processing multiple files together