将类型分配给Typescript中泛型映射函数的参数

type TypeName<T> =
  T extends string ? "string" :
  T extends number ? "number" :
  T extends boolean ? "boolean" :
  T extends undefined ? "undefined" :
  T extends Function ? "function" :
  "object";

function getTypeName<T>(param: T): TypeName<T> {
  return typeof param as TypeName<T>;
}

console.log(getTypeName("Hello"));  // Output: "string"
console.log(getTypeName(123));  // Output: "number"
console.log(getTypeName(true));  // Output: "boolean"
console.log(getTypeName(undefined));  // Output: "undefined"
console.log(getTypeName(() => {}));  // Output: "function"
console.log(getTypeName({}));  // Output: "object"