A structured lesson workspace with readable content, hands-on examples, and a clean path to completion.
| Observation | Diagnostic question |
|---|---|
| Runtime value | What value actually arrived? |
| Language rule | Which rule determines the result? |
const result = Promise.resolve(21).then(value => value * 2).catch(error => console.error(error));result.then(console.log);
This example demonstrates promise chaining and error handling directly. Change one input at a time and observe the result; the goal is to connect the syntax to the runtime behavior rather than treating the snippet as a recipe.
A common failure with promise chaining and error handling is changing several variables at once. That hides which rule actually caused the result.
Finish the lesson once you have worked through the material. This awards ★ 20 XP.