requireNonString

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

The test is typeof value === "string", so the empty string passes and a String object, being an object, does not.

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

Returns

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

Throws

Exception	Condition
`IllegalArgumentException`	the value is a string.

Examples

What passes and what does not

requireNonString(1); // => 1
requireNonString(null); // => null
requireNonString(""); // throws IllegalArgumentException
requireNonString("abc"); // throws IllegalArgumentException

Source

src/lang/base/requireNonString.ts

23 September 2026

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

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