@openreachtech/mentsu-value-inspector

Readable predicate methods for inspecting JavaScript values (numbers, integers, dates), backed by pluggable normalizers.

Each inspector wraps a single value and exposes self-describing checks — isNumber(), isPositiveNumberLike(), isDate(), and so on — so scattered, error-prone type checks can be replaced with a consistent API.

Concept

Inspectors provide two families of predicates:

• Strict predicates check the raw JavaScript value as-is (isNumber(), isInteger(), isDate()).
• *Like predicates first normalize the value, so loosely-typed inputs such as numeric strings are accepted (isNumberLike(), isIntegerLike(), isDateLike()).

Normalization is delegated to a normalizer from @openreachtech/mentsu-value-normalizer. A default normalizer is created per inspector, but you may inject your own.

Installation

Requires Node.js 20.x (the version the CI builds against).

npm install @openreachtech/mentsu-value-inspector

It is an ES module ("type": "module"); import it with ESM import syntax.

Usage

import {
  NumberValueInspector,
  IntegerValueInspector,
  DateValueInspector,
} from '@openreachtech/mentsu-value-inspector'

// Numbers: strict vs. *Like
const numberInspector = NumberValueInspector.create({ value: '42' })

numberInspector.isNumber() // false (the raw value is a string)
numberInspector.isNumberLike() // true  (the string is normalized to a number)

NumberValueInspector.create({ value: -3 }).isNegativeNumber() // true
NumberValueInspector.create({ value: '1.5' }).isPositiveNumberLike() // true

// Integers
const integerInspector = IntegerValueInspector.create({ value: '10' })

integerInspector.isInteger() // false (the raw value is a string)
integerInspector.isIntegerLike() // true
IntegerValueInspector.create({ value: 10.5 }).isSafeInteger() // false

// Dates
const dateInspector = DateValueInspector.create({ value: '2020-01-01' })

dateInspector.isDate() // false (the raw value is a string)
dateInspector.isDateLike() // true
DateValueInspector.create({ value: new Date('invalid') }).isDate() // false

API

See the API reference.

Contribution

Bug reports, feature requests, and code contributions are welcome.

Feel free to contact us through GitHub Issues.

git clone https://github.com/openreachtech/mentsu-value-inspector.git
cd mentsu-value-inspector
npm install
npm run lint
npm test

License

This project is released under the Apache License 2.0.

For more details, please see in the LICENSE file.

Developer

Open Reach Tech Inc.

Copyright

© 2026 Open Reach Tech Inc.