function isString isString(s: unknown): s is string Type guard to check if a value is a string. Handles both string primitives and String objects. Examples Type narrowing import { isString } from "jsr:@j50n/proc"; const value: unknown = "hello"; if (isString(value)) { // TypeScript knows value is string here console.log(value.toUpperCase()); } Parameters s: unknown The value to check. Return Type s is string True if the value is a string.