如何使用typeof来获取对象的“运行时”类型？

function getType(obj) {
  return typeof obj;
}

console.log(getType(undefined));  // 输出 "undefined"
console.log(getType(true));       // 输出 "boolean"
console.log(getType(123));        // 输出 "number"
console.log(getType("hello"));    // 输出 "string"
console.log(getType(Symbol()));   // 输出 "symbol"
console.log(getType(function(){}));// 输出 "function"
console.log(getType({}));         // 输出 "object"
console.log(getType([]));         // 输出 "object"
console.log(getType(new Date())); // 输出 "object"
console.log(getType(/regex/));    // 输出 "object"