JSPM – ow@0.2.0

Package Exports

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (ow) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

Argument type validation

View documentation

Install

$ npm install ow

Usage

import ow from 'ow';

const unicorn = input => {
    ow(input, ow.string.minLength(5));

    // …
};

unicorn(3);
//=> ArgumentError: Expected argument to be of type `string` but received type `number`

unicorn('yo');
//=> ArgumentError: Expected string to have a minimum length of `5`, got `yo`

API

ow(value, predicate)

Test if value matches the provided predicate.

ow.create(predicate)

Create a reusable validator.

const checkPassword = ow.create(ow.string.minLength(6));

checkPassword('foo');
//=> ArgumentError: Expected string to have a minimum length of `6`, got `foo`

ow.any(...predicate[])

Returns a predicate that verifies if the value matches at least one of the given predicates.

ow('foo', ow.any(ow.string.maxLength(3), ow.number));

ow.{type}

All the below types return a predicate. Every predicate has some extra operators that you can use to test the value even more fine-grained.

Primitives

Built-in types

Typed arrays

Structured data

Miscellaneous

Predicates

The following predicates are available on every type.

not

Inverts the following predicates.

ow(1, ow.number.not.infinite);

ow('', ow.string.not.empty);
//=> ArgumentError: [NOT] Expected string to be empty, got ``

is(fn)

Use a custom validation function. Return true if the value matches the validation, return false if it doesn't.

ow(1, ow.number.is(x => x < 10));

ow(1, ow.number.is(x => x > 10));
//=> ArgumentError: Expected `1` to pass custom validation function

Instead of returning false, you can also return a custom error message which results in a failure.

const greaterThan = (max: number, x: number) => {
    return x > max || `Expected \`${x}\` to be greater than \`${max}\``;
};

ow(5, ow.number.is(x => greaterThan(10, x)));
//=> ArgumentError: Expected `5` to be greater than `10`

Maintainers

@sindresorhus/is - Type check values

License

MIT

ow