Types, at runtime.
TypeRun is a fast, lightweight, DX-focused, fully tested, dependency-free validation library that works everywhere JS can run. It allows you to define data schemas, then validate these against unknown data, and infer TypeScript types from them.
import { is } from "typerun";
import { object, number, string, array, Infer } from "typerun/schema";
const postSchema = object({
id: number,
title: string,
tags: array(string),
});
type Post = Infer<typeof postSchema>;
const post = {
id: 1,
title: "Hello, world!",
tags: ["dev", "blog"],
};
function getPostTitle(post: Post) {
return post.title;
}
if (is(postSchema)(post)) {
console.log(getPostTitle(post)); // "Hello, world!"
}Install TypeRun from npm using your project’s package manager.
pnpm add typerun
npm install typerun
bun install typerun
yarn add typerun
deno install npm:typerunThen, define a schema (= a type) for a resource, using TypeRun’s straightforward syntax.
import { object, number, string, optional, either, value } from "typerun/schema";
const userSchema = object({
id: number,
email: string,
name: optional(string),
role: either(value("admin"), value("user")),
});Schemas can be the single source of truth for your data types, using the Infer utility type:
import { Infer } from "typerun/schema";
type User = Infer<typeof userSchema>;
/* ^? type User = {
id: number;
email: string;
name: string | undefined;
role: "admin" | "user";
}
*/You can then validate some unknown data to be of the correct type, in a safe, non-throwing way:
import { validate } from "typerun";
import { isOk } from "typerun/result";
const unknownData: unknown = await fetchUser(42);
const userResult = validate(userSchema)(unknownData);
if (isOk(userResult)) {
console.log(userResult.email);
} else {
console.error(userResult.errors);
}You can also do it with a throwing function:
import { validate } from "typerun";
const unknownData: unknown = await fetchUser(42);
try {
const user = validate(userSchema, { throwing: true })(unknownData);
console.log(user.email);
} catch (errors) {
console.error(errors);
}The typerun package exports 4 entrypoints, namely:
typerun: Validation functionstyperun/parse: JSON-parsing helpertyperun/schema: Schema definition functionstyperun/result: TheResulttype, and utility functions to handle it.
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