type-validation-ts

This CLI generates type-guard validator functions from typescript types. It generates JSON schemas from typescript types with typescript-json-schema and then generates type-guard functions which validate unknown objects with those schemas.

How it works

interface HelloWorld {
  foo: string
  bar: number
}

function loadWorld(data: unknown) {
  if(isHelloWorld(data)) { // generated validator function
    console.log(data.foo, data.bar) // type-safe access to data.foo and data.bar
  }
}

Create a .ts file where you export all the types you want to generate vaildators for.

export { Foo, Bar } from './path/to/module'
export { Foo2, Bar2 } from './path/to/module2'

To generate the validator functions run

generate-validators ./path/to/types.ts ./out/path/to/validators

You can now use the validator functions in your project (eg. an express server):

import { isFoo, isBar } from './out/path/to/validators'

const app = new Express()

app.post('/foo', (req, rsp) => {
  if(!isFoo(req.body)) {
    rsp.status(400).send('Body is in wrong format!')
    return
  }
  // continue with type-safe access to req.body
})

Setup

First, install the type-validation-ts package with npm install type-validation-ts -D

Then you have to install the jsonschema package because the generated validate functions require it.

npm install jsonschema