TypeScript for APIs · Backend Development

Explanation

Type request bodies, database models, and responses so backend bugs show up at compile time.

Code example

typescript

type CreateSkillInput = { name: string; level: "beginner" | "advanced" };

export function parseSkill(body: unknown): CreateSkillInput {
  if (!body || typeof body !== "object" || !("name" in body)) {
    throw new Error("Invalid payload");
  }
  const name = String((body as { name: unknown }).name);
  return { name, level: "beginner" };
}

Helpful resources

TypeScript Handbook
Official TypeScript documentation.
DocumentationFreeOfficial90 min
TypeScript course — freeCodeCamp
TypeScript for beginners on YouTube.
YoutubeFree90 min

Exercise

Type a create-user payload and a User model, then write a parser that rejects invalid JSON.

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