function assertnumber assertnumber(x: unknown): asserts x is number Asserts that a value is a number. Throws a TypeError if the input is not a number. Uses TypeScript's type assertion to narrow the type. Examples Valid number import { assertThrows } from "jsr:@std/assert"; assertnumber(5); // No error Invalid input throws error import { assertThrows } from "jsr:@std/assert"; assertThrows(() => assertnumber("5"), TypeError, "Expected number, got string"); NaN is a valid number import { assertThrows } from "jsr:@std/assert"; assertnumber(NaN); // No error Parameters x: unknown The value to check Return Type asserts x is number Throws If x is not a number