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Zod Lite

A Learning TypeScript > Type Operations 🍲 entree project.

Kneel before Zod!

General Zod of the Kryptonian Army demands your assistance in creating a Zod-like schema validation library. It must support strings, literal strings, unions of literal strings, and objects with properties that can be any of the above. Only in this way will the former glory of the Kryptonian Army be restored.

Setup​

If you haven't yet, set up the github.com/LearningTypeScript/projects repository locally.

shell
git clone https://github.com/LearningTypeScript/projects learning-typescript-projects
cd learning-typescript-projects
npm i
shell
git clone https://github.com/LearningTypeScript/projects learning-typescript-projects
cd learning-typescript-projects
npm i

Open your editor in this project's directory:

shell
code projects/type-operations/zod-lite
shell
code projects/type-operations/zod-lite

In one terminal, run the TypeScript compiler via the tsc script. For example, to start the TypeScript compiler in watch mode:

shell
npm run tsc -- --watch
shell
npm run tsc -- --watch

In another terminal, run Jest via the test script. For example, to start tests in watch mode:

shell
npm run test -- --watch
shell
npm run test -- --watch

Specification​

Create and export the following functions from src/index.ts:

  • string(): creates a schema object representing any primitive string
  • literal<Value>(value): creates a schema object of a literal string value
  • union<Values>(values): creates a schema object representing multiple allowed type constituents
  • object<Properties>(properties): creates a schema object representing an object

Additionally, export an type Infer<Schema> that creates a TypeScript type for a schema.

Example​

Given this code:

ts
import * as z from "./index";
const spySchema = z.object({
	disguise: z.string(),
	trueName: z.literal("Kal-El"),
	role: z.union([z.literal("hero"), z.literal("reporter")]),
});
type Spy = z.Infer<typeof spySchema>;
ts
import * as z from "./index";
const spySchema = z.object({
	disguise: z.string(),
	trueName: z.literal("Kal-El"),
	role: z.union([z.literal("hero"), z.literal("reporter")]),
});
type Spy = z.Infer<typeof spySchema>;

The Spy type should be equivalent to:

ts
type Spy = {
	disguise: string;
	trueName: "Kal-El";
	role: "hero" | "reporter";
};
ts
type Spy = {
	disguise: string;
	trueName: "Kal-El";
	role: "hero" | "reporter";
};

Note: your terminal should be in the zod-lite directory, not the root repository's directory.

If you are not familiar with the glory of General Zod or the Zod schema library named after him, you can read the Zod basics documentation to learn more about how it works.