fan.js is a implementation of the Promise/A+ spec written in ES5. It uses a simple and easy-to-understand style that closely matches every line of the spec. fan.js is a good example to reference when creating your own Promise and to help you learn the Promise/A+ spec.

Live Demo

• Read the specification with use cases. Do it again if you have no idea how to begin.
• Define the Promise class or constructor.
• Make the Promises/A+ Compliance Test Suite works well with your code.
• Define the then() method.
• Implement chaining.
• Handle errors.

fan.js has passed all the tests in the Promises/A+ Compliance Test Suite.

To run all the tests, use the following command:

npm run test

The Promises/A+ Compliance Test Suite organizes tests by spec requirements. If you want to run the tests for a specific requirement, use a command like:

npm run test -- grep 2.1.2

• Promise() constructor
• fan.js history
• Promises/A+ Compliance Test Suite