never

A function that throws when called, use with nullish coalescing to elide unexpected nullish values.

But why?

Sometimes you have a function which in theory may return undefined or null, except you're already really sure that it doesn't. Explicitly guarding against those unlikely values is cumbersome. In TypeScript you could use the non-null assertion (!) but that's very subtle.

Use never() instead! It always throws when called, so when used with the nullish coalescing operator, TypeScript will elide the undefined or null types:

const never = require('never')

function getValue (): string | undefined {
  // ...
}

function setString (value: string): void {
  // ...
}

const value = getValue() ?? never('Despite the type, in practice a value is always returned')
setString(value) // Works!

Installation

npm install never

Usage

const never = require('never')

// Throw with a default message:
never()

// Throw with your own message:
never('Your own message')

never() throws an AssertionError.