ts-blaze

This library makes type-safe usage of objects from unknown origin (-> api payloads, events, parsed files etc.) a blast. It does so by generating typeguards for the validators you create.

Usage

import * as blaze from 'ts-blaze'

const isHuman = blaze.object({
  name: blaze.string(),
  age: blaze.optional(
    blaze.number()
      .satisfies(val => val >= 0)
  )
})
type Human = blaze.InferValidatorType<typeof isHuman>

export const onlyAcceptHumans = (payload: any): Promise<Human> => {
  // throw if payload doesn't match schema
  const human = blaze.ensure(payload, isHuman) 

  // now your IDE/Editor can also complete this
  console.log(`Creating human with name "${human.name}".`)
  return db.createHuman(payload)
}

export const handleBadInput = (payload: any): Promise<Human | void> => {
  if (isHuman(payload)) {
    // typeguarded -> typeof payload is Human
    return db.createHuman(payload)
  }

  console.warn('Did not receive a human.')
  return Promise.resolve()
}

Details

The object validator matches standard TypeScript behaviour, i.e. it doesn't complain about additional keys.

Provided Types

Currently the following types are supported: object, array, string, number, oneOf([ ...unionTypes ]), undefined, null, any, record, string literal (using string('literal')) and number literal (using number(1)).

Options

Every type except the literal types support .satisfies(predicate: (value: T) => boolean). In addition string supports .json() using JSON.parse(...) for validation. The object type supports .exact(), not allowing the object to have additional keys. You can overwrite JSON.parse(...) while validating in order to not have to parse complex JSON multiple times (once for validation and once for usage) or use a custom .satisfies(...) predicate for that.

Define Your Own

import * as blaze from 'ts-blaze'
import { validate: isUuid } from 'uuid'

export const uuid = blaze.string()
  .satisfies(isUuid)

Error Messages

At the moment there are no plans to implement validation error messages. However I'm open to ideas so feel free to create issues and PRs for this as well.