JavaScript Promises Explained: .then(), .catch() & Promise Chaining | QA Thoughts
Are you struggling with nested functions and the "Pyramid of Doom"? In this video, we learn how to use JavaScript Promises to fix "Callback Hell" and write clean, maintainable asynchronous code.
We start by understanding why Callbacks become unmanageable and how Promises solve this using the Chaining technique.
Topics Covered in this Video:
00:00 - Introduction: The problem with Asynchronous code
00:24 - What is Callback Hell (Pyramid of Doom)?
01:11 - What is a Promise? (Pending, Resolved, Rejected)
01:29 - Creating a Promise: resolve and reject
02:09 - Consuming Promises: Using .then(), .catch(), and .finally()
03:15 - Real World Example: "Buying a Bike" Logic
07:26 - Refactoring Code: Converting Nested Callbacks to Promises
12:42 - Promise Chaining: How to execute tasks sequentially
🛠️ Concept Explained:
A Promise is an object representing the eventual completion (or failure) of an asynchronous operation.
Resolve: The operation was successful.
Reject: The operation failed (Error handling).
Chaining: Connecting multiple .then() blocks to run functions one after another.
💡 Why is this important for QA?
Before you can use modern tools like Playwright or Cypress, you must understand Promises. This is the foundation of handling API responses, database queries, and timeouts in your test scripts.
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Quick Summary:
This video explains about how to create promise and how to consume promise in javascript. It also explains about how to convert callback functions to promises & then use promise chaining to get out of callback hell.
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