Promises

Testing Async Code: Promises and async/await

Learn the correct patterns for testing promise-based and async/await code in Jest, and the pitfalls that let async bugs slip past a green test run.

Promises in JavaScript

Understand the Promise object, its three states, and how .then/.catch/.finally chaining replaces nested callbacks.

Promises in Node.js

Understanding the Promise object and its pending, fulfilled, and rejected states for cleaner async code.

JavaScript Error Handling Cheat Sheet

Covers try/catch/finally, custom Error subclasses, handling errors in promises and async/await, and the ES2022 error cause chain.

Promises vs async/await: What Is the Difference?

Promises and async/await are the same underlying mechanism for handling asynchronous results — async/await is syntactic sugar built on top of Promises that let…

Microtask vs Macrotask Queue: What Is the Difference?

The microtask queue holds high-priority callbacks like Promise .then() handlers and queueMicrotask(), which the event loop fully drains after every single sync…

How Does the Event Loop Order Microtasks and Macrotasks?

After each single macrotask finishes executing, the event loop fully drains the entire microtask queue — including any new microtasks scheduled during that dra…

Promise.all vs Promise.allSettled: When to Use Each?

Promise.all resolves with an array of values only if every input promise fulfills, and it rejects immediately with the first rejection reason if any one fails,…

Promise.race vs Promise.any: What Sets Them Apart?

Promise.race settles as soon as any one input promise settles — whether it fulfills or rejects — mirroring whatever that first promise did, while Promise.any s…