Enums vs const enum vs union-literal alternatives
Compare classic enums, const enums, and union-literal alternatives; learn trade-offs for DX, size, and safety.
Enums vs const enum vs union-literal alternatives is a free TypeScript Academy lesson on CoddyKit. This is lesson 3 of 3. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the TypeScript Academy learning path, and your progress syncs across the web and the CoddyKit app. The TypeScript Academy course includes 3 lessons in total.
Intro
Goal: See when to use enum, const enum, or union-literal types. You'll compare runtime output, DX, and tree-shaking.
Numeric enum
Numeric enums emit a runtime object and allow reverse mapping. Simple, but they add some bundle size.
enum Direction {
Left = 0,
Right = 1
}
const d: Direction = Direction.Left;
console.log(d); // 0String enum
String enums are readable in logs and APIs. They also emit runtime objects.
enum Status {
Ok = "ok",
Error = "error"
}
const s: Status = Status.Ok;
console.log(s); // "ok"const enum
const enum inlines values at compile time for zero runtime cost, but requires consistent build tooling.
const enum Axis {
X = 0,
Y = 1
}
const a: Axis = Axis.X;
console.log(a); // 0 (inlined)Union-literal alternative
Union-literals: no runtime output, great narrowing in switch, and excellent tree-shaking. Great default for many cases.
type Dir = "left" | "right";
function move(d: Dir) {
switch (d) {
case "left":
console.log("←");
break;
case "right":
console.log("→");
break;
}
}
move("left");When to choose
Guidelines:
- Prefer union-literals for most option sets (no runtime cost).
- Use enum if you need a runtime object or reverse mapping.
- Use const enum for inlined constants when your build supports it.
Union-literal vs enum check
Quick check: Which statement is TRUE about union-literal types as an alternative to enums?
Recap
Recap: enum creates runtime objects; const enum inlines values for zero cost; union-literals give safety with no runtime output. Choose based on your build and API needs.
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Frequently Asked Questions
Is the “Enums vs const enum vs union-literal alternatives” lesson free?
Yes — the full text of “Enums vs const enum vs union-literal alternatives” is free to read here on the web. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the TypeScript Academy course, upgrade to CoddyKit PRO. The TypeScript Academy course includes 3 lessons in total.
What will I learn in “Enums vs const enum vs union-literal alternatives”?
Compare classic enums, const enums, and union-literal alternatives; learn trade-offs for DX, size, and safety. You practise TypeScript Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start TypeScript Academy?
No prior experience is required. TypeScript Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 3 of 3.
How long does the “Enums vs const enum vs union-literal alternatives” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this TypeScript Academy lesson?
Yes. Every TypeScript Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Arrays & ReadonlyArray
- Tuples & labeled tuples
- Enums vs const enum vs union-literal alternatives