A structured lesson workspace with readable content, hands-on examples, and a clean path to completion.
| Question to ask | Good diagnostic move |
|---|---|
| What value entered? | Inspect the runtime value and type. |
| What rule applied? | Check the construct's language or host semantics. |
| What changed? | Compare the smallest working and failing cases. |
const instant = new Date('2026-08-22T18:00:00Z');console.log(instant.toISOString());
<strong>Core idea:</strong> The deeper object model explains why two variables can appear independent while changing the same value underneath. These lessons focus on references, built-in collections, and structured data. In this lesson, the practical target is dates and time handling: you should be able to predict what the runtime will do before changing the code.
<strong>Core idea:</strong> The deeper object model explains why two variables can appear independent while changing the same value underneath. These lessons focus on references, built-in collections, and structured data. In this lesson, the practical target is dates and time handling: you should be able to predict what the runtime will do before changing the code.
Mentor note: for dates and time handling, name the invariant you need before reaching for a clever shortcut. Clear state and explicit assumptions make later debugging much cheaper.
Finish the lesson once you have worked through the material. This awards ★ 20 XP.