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Loom

Loom Schema

Loom Schema is a lightweight toolkit for composing JSON Schema definitions in a fluent manner and validating data against those schemas. It uses AJV under the hood to perform validation, but abstracts away much of the complexity. You can define schemas for your data, then either compile and validate against them or export them as standard JSON Schemas.

Features

  • Easy Schema Composition: Write and reuse fragments for strings, numbers, arrays, objects, etc.
  • Built-in Validation: Any schema fragment can validate data directly, returning helpful errors if the validation fails.
  • AJV Integration: Fine-tune validation with AJV’s options, custom keywords, or custom vocabularies.
  • TypeScript-Friendly: Infer TypeScript types from your Loom schemas, ensuring that your data usage aligns with the rules you set.

Installation

Terminal window
bun install loom-schema

Basic Usage Example

import { object, string, number, Infer } from "loom-schema";


// Define a schema fragment for a user object
const userSchema = object({
  properties: {
    name: string({ minLength: 1 }),
    age: number({ minimum: 0 }),
  },
  required: ["name", "age"],
});


// Validate some data
async function runExample() {
  const result = await userSchema.validate({ name: "Alice", age: 25 });
  if (result.valid) {
    console.log("Data is valid!");
  } else {
    console.error("Validation errors:", result.errors);
  }
}


runExample();


// Infer TypeScript types from your schema
type User = Infer<typeof userSchema>;

In the snippet above:

  • We create a simple user schema describing an object with two properties (name and age).
  • We call .validate(...) on the schema to check if a sample data object is valid.
  • We also demonstrate how to use the Infer utility type to derive a TypeScript type from our schema.

Continue to the API Reference for details on each helper function.