执行以下代码，正确的输出结果是：console.log(Ob

[单选题]

执行以下代码，正确的输出结果是：console.log(Object.prototype.toString.call(undefined))

```
[Object Undefined]
```
```
"[object Undefined]"
```
```
[object Undefined]
```
```
[object undefined]
```

查看答案及解析

MaDic6

用 typeof 是否能准确判断一个对象变量，答案是否定的，null 的结果也是 object，数组的结果也是 object，有时候我们需要的是 "纯粹" 的 object 对象。如何避免呢？比较好的方式是：

console.log(Object.prototype.toString.call("jerry"));//[object String]

console.log(Object.prototype.toString.call(12));//[object Number]
console.log(Object.prototype.toString.call(true));//[object Boolean]
console.log(Object.prototype.toString.call(undefined));//[object Undefined]
console.log(Object.prototype.toString.call(null));//[object Null]
console.log(Object.prototype.toString.call({name: "jerry"}));//[object Object]
console.log(Object.prototype.toString.call(function(){}));//[object Function]
console.log(Object.prototype.toString.call([]));//[object Array]
console.log(Object.prototype.toString.call(new Date));//[object Date]
console.log(Object.prototype.toString.call(/\d/));//[object RegExp]
function Person(){};
console.log(Object.prototype.toString.call(new Person));//[object Object]

发表于 2021-04-20 17:27:39 回复(0)