requireState

function requireState(condition: unknown, message?: string): asserts condition;

For the checks that are about the moment rather than the arguments: a connection that is already closed, a sheet that has not been prepared yet, a value that was supposed to be cached by now.

It is declared as a TypeScript assertion, so after the call the compiler treats the condition as true for the rest of the function.

Parameters

Parameter	Type	Description
`condition`	`unknown`	The condition that must hold.
`message` (optional)	`string`	The message of the exception. A default is used when omitted.

Returns

asserts condition — nothing; it either passes or throws.

Throws

Exception	Condition
`IllegalStateException`	the condition is falsy.

Examples

Guarding a state

function close(connection) {
  requireState(connection.isOpen, "The connection is already closed.");

  connection.release();
}

Source

src/lang/base/requireState.ts

23 September 2026

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

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