requireEmpty

function requireEmpty<T>(
  value: T,
  message: string = "Expected an empty value.",
  strict: boolean = false
): T;

Emptiness is read per kind: null and undefined, a string with nothing but whitespace, an array, Set or Map with no entries, an object with no own keys. 0 and false are values, not emptiness.

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`	The value to validate.
`message` (optional) `= "Expected an empty value."`	`string`	The message of the exception. A default is used when omitted.
`strict` (optional) `= false`	`boolean`	When `true`, a string counts as empty only if it has no characters at all; by default whitespace is trimmed first.

Returns

T — the same value, typed as an empty value.

Throws

Exception	Condition
`IllegalArgumentException`	the value is not empty.

Examples

What passes and what does not

requireEmpty(null); // => null
requireEmpty(""); // => ""
requireEmpty(0); // throws IllegalArgumentException
requireEmpty(false); // throws IllegalArgumentException

Source

src/lang/base/requireEmpty.ts

23 September 2026

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

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