typd

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

Table of contents

• Install
• Use
• Examples
• Contributing
• Thanks
• License

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:

• Typd.any
• Typd.none
• Typd.boolean
• Typd.Boolean
• Typd.string
• Typd.String
• Typd.number
• Typd.Number
• Typd.Object
• Typd.function matches any function

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 => {/* ... */}
);

Contributing

Please read the contribution guidelines. Contributions are welcome!

Thanks

Thanks to those who work on typecheck, without whom this would have been a lot more work.

License

Copyright (c) 2015 Tom Ashworth. Released under the MIT license.