Literal Types

This lesson covers literal types, which use a specific value itself as a type. It's for anyone searching "TypeScript literal type."

A string or number itself can be used directly as a type, and combined with a union type, you can create a type that "only allows a fixed set of values." For example, writing "small" | "medium" | "large" means nothing but those three strings can be assigned.

The example defines type Size = "small" | "medium" | "large"; and builds a function returning a different price per size. Passing a value that doesn't exist (like "huge") produces a compile error.

A common early mistake is not seeing the difference from a plain string type. A string type accepts any string at all, while a literal type's big difference is that it rejects anything outside the fixed set of candidates.

In real projects, literal types are used a lot for fields with a fixed set of possible values, like an order size or a status ("in progress," "complete," and so on).

📖 Reference code

type Size = "small" | "medium" | "large";

function priceOf(size: Size): number {
  const prices: Record<Size, number> = { small: 300, medium: 400, large: 500 };
  return prices[size];
}
console.log(`Medium size: ${priceOf("medium")}`);

✍️ Your code

Type your code, then press "Run"

🧪 This site can't compile or run TypeScript directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).