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Lesson 9 — Enums
Named constants
An enum groups related constants under readable names. By default the members are numbered from 0: in enum Size { S, M, L }, Size.M is 1. Number enums also have a reverse mapping — Size[1] gives back the name "M".
enum Size { S, M, L }
const pick = Size.L; // 2
console.log(Size[pick]); // L
Why it matters: Direction.Left is clearer and safer than a magic number 2 scattered around your code.
Want it another way?
Task
Log the number stored in Direction.Left, then the name for the number 1. Expect 2, then Down.
Run your code — when the output matches the task, you will see a green check. Then mark the lesson complete.
Test your knowledge
Test your knowledgeA quick 3-question quiz on this lesson — instant feedback.