@quentinadam/ensure

A simple function that asserts that a value is not undefined or null and returns the narrowed value.

Usage

import { AssertionError, ensure } from '@quentinadam/ensure';

const a = ensure(1); // returns 1

try {
  const b = ensure(undefined);
} catch (e) {
  // throws AssertionError
}

try {
  const c = ensure(undefined, 'Value is required');
} catch (e) {
  // throws AssertionError with custom message
}

try {
  const d = ensure(undefined, new Error('Value is required'));
} catch (e) {
  // throws a custom Error
}

const value: string | undefined = 'hello';
const narrowedValue = ensure(value); // narrows the type to string
narrowedValue.toUpperCase(); // works