toString()的基于条件的返回

function toStringBasedOnCondition(obj) {
  if (obj instanceof Array) {
    return "This is an array: " + obj.toString();
  } else if (typeof obj === "object") {
    return "This is an object: " + JSON.stringify(obj);
  } else {
    return "This is a primitive value: " + obj.toString();
  }
}

var arr = [1, 2, 3];
var obj = { name: "John", age: 30 };
var num = 42;

console.log(toStringBasedOnCondition(arr)); // 输出：This is an array: 1,2,3
console.log(toStringBasedOnCondition(obj)); // 输出：This is an object: {"name":"John","age":30}
console.log(toStringBasedOnCondition(num)); // 输出：This is a primitive value: 42