JavaScript: Mental Models & Labs

Each lab follows the same shape, in order:

1. One mental model
2. What the engine is doing internally
3. A tiny experiment
4. Predict before running (when relevant)
5. Run it
6. Explain the result — what you wrote vs what the engine effectively does
7. Change one thing
8. Predict again
9. Connect it back to the mental model
10. A tiny comprehension check

Not a syntax reference, not an app-building tutorial, not gated behind quizzes to advance. Experiments stay intentionally small — the goal is understanding why JavaScript behaves the way it does, not shipping a project. Skip around if a later lab pulls you in; just make sure any prerequisite concepts it names are ones you've already done.