Summary  
This chapter explains how to create a custom Promise that resolves or rejects based on a condition and how to handle its outcome using `.then` and `.catch`.  

General domain of usage  
Asynchronous operations

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When you create a custom Promise like `checkNumber`, you can control how and when it resolves or rejects. The function above returns a new Promise that checks if a given number is greater than 10. If the condition is met, it calls `resolve` with a success message; otherwise, it calls `reject` with an error message. To handle the outcome of this Promise, you use the `.then` method to respond to a successful resolution, and the `.catch` method to handle a rejection. For instance, calling `checkNumber(15)` would trigger the `.then` block, while `checkNumber(5)` would trigger the `.catch` block. This pattern helps you manage asynchronous results and errors in a clean and predictable way.

Which method is used to handle a rejected Promise?

Master the core concepts of asynchronous programming in JavaScript, from the event loop to modern async/await syntax. Learn how JavaScript handles non-blocking operations, why asynchronous code is essential, and how to write robust, readable, and maintainable asynchronous code using Promises and async/await.

Explore why asynchronous programming is necessary in JavaScript, how it differs from synchronous code, and the mechanics of the event loop and callback queue.

Learn how Promises provide a cleaner, more manageable way to handle asynchronous operations, including creation, chaining, and combinator methods.

Discover how async/await syntax simplifies asynchronous code, making it more readable and maintainable.

Learn how to handle and debug asynchronous errors, avoid common pitfalls, and write predictable, non-blocking JavaScript code.

Creating Custom Promises

Creating Custom Promises