@causaly/isnt

@causaly/isnt

A collection of common runtime predicates that TypeScript actually understands.

Features

• Simple API;
• Extensive tests;
• Isomorphic library, works on the browser or Node.js.

Installation

npm install @causaly/isnt

Requirements

• Node.js v.14+

Quick start

import { isNotNull } from '@causaly/isnt';

// given an array containing null and number values
const array = [1, 2, null]; // ts infers Array<null | number>

// ...remove null values by using isNotNull
const arrayWithoutNull = array.filter(isNotNull); // ts infers Array<number>

API

• isNotEmptyArray
• isNotEmptyString
• isNotNull
• isNotUndefined

Motivation

It's easy to perform a check using lodash or vanilla JavaScript, e.g.

const array = [1, 2, null].filter(Boolean);

The example above will filter out the null value as expected (because null is considered to be faulty).

However, TypeScript will NOT infer the correct type [playground link]. It will understand the type of array as being Array<null | number> instead of Array<null>.

@causaly/isnt provides a simple API to test for predicates, while making TypeScript understand.

Contribute

Source code contributions are most welcome, as long as the linter is satisfied.

We are hiring

Causaly is building the world's largest biomedical knowledge platform, using technologies such as TypeScript, React and Node.js. Find out more about our openings at https://apply.workable.com/causaly/.

License

MIT