vator

Assert validator for TypeScript projects.

Installation

npm install vator

Usage

// ESM or TypeScript projects:
import { v, validate, buildSchema, is } from 'vator';

// CommonJS projects:
const { v, validate, buildSchema, is } = require('vator');

Examples

'is'

is is a collection of shortcuts for comparing types of values. The regular

if (value === undefined) {
  ...
}

can be replaced with more convenient

if (is.undefined(value)) {
  ...
}

Designed to be used in conditions, because it uses type guard approach.

const maybeNumber = Math.random() > 0.5 ? 10 : null;

if (is.number(maybeNumber)) {
  // TS will not complain, because maybeNumber is number already
  console.log(maybeNumber + 10); // 20
} else {
  console.log(maybeNumber === null); // true
}

Available is validators:

is.undefined();
is.null();
is.nullable();
is.string();
is.number();
is.email();
is.phone();

Primitives with 'validate'

Will validate that value is a string type:

const value = 'some';

validate(value, v.string);

Will throw an error if value is not matching the type:

const value = 22;

validate(value, v.string);

Error:

Validation failed: value has type 'number', but 'string' type is required.

Objects and Arrays with 'validate'

Will validate that value is an object with described fields. Also it's more convenient to use buildSchema helper to get schema and ResultType.

Note

ReturnType is an empty object, only refers to valid result type!.

// Let's pretend that 'value' is 'unknown' type
const value: unknown = {
  name: 'some-name',
  age: 100,
  isOnline: false,
  updatedAt: '2023-05-22T14:32:34.324Z',
  unknownData: [2, 'foo', false]
  cars: [
    {
      model: 'bmw',
      year: 2017
    },
    {
      model: 'audi',
      year: null
    }
  ]
};

const { schema, ResultType } = buildSchema({
  name: v.string,
  age: v.optional.number,
  isOnline: v.maybe.boolean,
  updatedAt: v.Date,
  unknownData: v.unknown,
  cars: v.array(v.object({
    model: v.literal('bmw', 'audi'),
    year: v.nullable.number
  }))
});

validate(value, schema)

Also value will then have valid types (because validate() asserts them)