requireNonSymbol

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

Registered symbols from Symbol.for and the well-known symbols both pass; nothing else does.

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

Returns

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

Throws

Exception	Condition
`IllegalArgumentException`	the value is a symbol.

Examples

What passes and what does not

requireNonSymbol("id"); // => "id"
requireNonSymbol(null); // => null
requireNonSymbol(Symbol("id")); // throws IllegalArgumentException
requireNonSymbol(Symbol.iterator); // throws IllegalArgumentException

Source

src/lang/base/requireNonSymbol.ts

23 September 2026

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

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