requireNonNil

function requireNonNil<T>(
  value: T | null | undefined,
  message: string = "Expected a value that is neither null nor undefined."
): T;

The absent values, and only those: 0, "" and false are present values and do not qualify.

isX and nonX answer a question and never interrupt control flow; requireX and requireNonX hand the value back or throw. The scheme is explained in Validation conventions.

Parameters

Parameter	Type	Description
`value`	`T \\| null \\| undefined`	The value to validate.
`message` (optional) `= "Expected a value that is neither null nor undefined."`	`string`	The message of the exception. A default is used when omitted.

Returns

T — the same value, with null or undefined excluded from its type.

Throws

Exception	Condition
`IllegalArgumentException`	the value is `null` or `undefined`.

Examples

What passes and what does not

requireNonNil(0); // => 0
requireNonNil(""); // => ""
requireNonNil(null); // throws IllegalArgumentException
requireNonNil(undefined); // throws IllegalArgumentException

Source

src/lang/base/requireNonNil.ts

23 September 2026

This documentation was generated with AI (Claude) from the library's source code.

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