nullthrows

An idiomatic way to enforce values not to be null or undefined, with first-class support for TypeScript. Very lightweight with no dependencies.

Installation and usage

npm install @expo/nullthrows

import process from 'node:process';
import nullthrows from '@expo/nullthrows';

// nodeEnv is guaranteed to be a string. If the environment variable is
// undefined, nullthrows throws a TypeError.
const nodeEnv = nullthrows(process.env.NODE_ENV);

// You can optionally provide a custom error message
const nodeEnv2 = nullthrows(process.env.NODE_ENV, `NODE_ENV must be defined`);

API

function nullthrows<T>(value: T | null | undefined, message?: string): NonNullable<T>

Parameters

• value: the value to enforce not to be null or undefined
• message: an optional error message to use in the thrown TypeError if the given value is null or undefined

Type parameters

• T: the static type of value

Return value

Returns value if it is neither null nor undefined.

Throws

Throws a TypeError if value is null or undefined.

History

This package is a spiritual successor of nullthrows. The motivation for a new package was primarily to support using TypeScript with ES modules since the type declarations included with nullthrows produce type errors.