Function isPrimitive

isPrimitive(u: unknown): u is Primitive
Type guard that checks if a value is a primitive type.

This function identifies JavaScript primitive types, which are immutable data types that are not objects. The primitive types are: string, number, boolean, undefined, symbol, bigint, and null.

Important Note: Although null has typeof null === "object" due to a historical JavaScript quirk, this function correctly identifies null as a primitive value.

Type Narrowing Behavior:
- Narrows the input type to Primitive (union of all primitive types)
- Excludes object types, arrays, functions, and other non-primitive values
- Includes null despite its misleading typeof result
Parameters
- u: unknown
  The value to check
Returns u is Primitive
true if u is a primitive type, false otherwise. When true, TypeScript narrows the type to Primitive.
Example
```
const values: readonly unknown[] = [42, 'Ada', null, { id: 1 }] as const;

const primitives = values.filter(isPrimitive);

assert.deepStrictEqual(primitives, [42, 'Ada', null]);
```
- Defined in src/guard/is-primitive.mts:34