Typd NPM | npm.io

typd

Runtime type-checking for JavaScript. Mostly a wrapper around typecheck.

Install

npm install --save typd

Use

typd wraps functions to add runtime type-checks to them. The resulting function will throw if the arguments don't match.

import Typd from 'typd';

const add =
  Typd(
    ['a', Typd.number],
    ['b', Typd.number],
    (a, b) => a + b
  );

The Typd function takes any number of [string, function] tuples that represent argument name and the checker, and finally the function to be wrapped.

API

Here are the available checkers:

There are others that accept other checkers as arguments to create compound checkers:

Typd.arrayOf takes another checker, and matches arrays that contain elements that pass the supplied checker type. For example, Typd.arrayOf(Typd.boolean)
Typd.maybe takes another checker, matching that type or undefined. For example, Typd.maybe(Typd.boolean).
Typd.oneOf takes many checkers and makes sure one of them matches. For example, Typd.oneOf(Typd.string, Typd.String).
Typd.shape takes an object that describes the expected shape of the value. The values should be (any) other checkers. For example, Typd.shape({ a: Typd.number, b: Typd.maybe(Typd.arrayOf(Typd.string)) })

Examples

const { maybe, arrayOf, oneOf, string, number, shape } = Typd;

// Match two numbers and an optional options object
var f = Typd(
  ['a',    number],
  ['b',    number],
  ['opts', maybe(Typd.Object)],
  (a, b, opts={}) => {/* ... */}
);

// Match an optional array of either strings or numbers.
var f = Typd(
  ['args', maybe(arrayOf(oneOf(string, number)))],
  (args) => {/* ... */}
);

// Match a string and an optional callback function
var f = Typd(
  ['path', string],
  ['cb', maybe(Typd.function)],
  (path, cb) => {/* ... */}
);

// Match a user object
var f = Typd(
  ['user', Typd.shape({
    id: Typd.string,
    username: Typd.string,
    followers: Typd.number,
    contact: Typd.shape({
      emails: Typd.arrayOf(Typd.string),
      phones: Typd.arrayOf(Typd.string)
    })
  })],
  user => {/* ... */}
);