requireNonBoolean

function requireNonBoolean<T>(
  value: T | boolean,
  message: string = "Expected a non-boolean value."
): T;

Only the two primitives pass. new Boolean(false) is an object, and the strings "true" and "false" are strings.

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 \\| boolean`	The value to validate.
`message` (optional) `= "Expected a non-boolean value."`	`string`	The message of the exception. A default is used when omitted.

Returns

T — the same value, with a boolean excluded from its type.

Throws

Exception	Condition
`IllegalArgumentException`	the value is a boolean.

Examples

What passes and what does not

requireNonBoolean("true"); // => "true"
requireNonBoolean(1); // => 1
requireNonBoolean(true); // throws IllegalArgumentException
requireNonBoolean(false); // throws IllegalArgumentException

Source

src/lang/base/requireNonBoolean.ts

23 September 2026

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

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