Question

function Hero(name) {
    this.name = name;
}
var h = new Hero('Leonardo');
var a = h instanceof Hero;
var b = h instanceof Object;`

在这里，我可以理解一个将是真实的＆＃39;。但是当我在Firefox控制台中检查时，b也是真的＆＃39; true＆＃39;。为什么会这样？

Answer 1

对象是其原型链上所有内容的实例：

＆＃13;

function Animal() {
}

function Cat() {
}

function Dog() {
}

Cat.prototype = Object.create(Animal.prototype);
Dog.prototype = Object.create(Animal.prototype);

var felix = new Cat();
snippet.log("Felix");
snippet.log("Object - " + (felix instanceof Object));
snippet.log("Animal - " + (felix instanceof Animal));
snippet.log("Cat    - " + (felix instanceof Cat));
snippet.log("Dog    - " + (felix instanceof Dog));

snippet.log("-----------");

var spike = new Dog();
snippet.log("Spike");
snippet.log("Object - " + (spike instanceof Object));
snippet.log("Animal - " + (spike instanceof Animal));
snippet.log("Cat    - " + (spike instanceof Cat));
snippet.log("Dog    - " + (spike instanceof Dog));

＆＃13;

<!-- Provides the `snippet` object, see http://meta.stackexchange.com/a/242144/134069 -->
<script src="http://tjcrowder.github.io/simple-snippets-console/snippet.js"></script>

＆＃13;

Answer 2

归因于Prototype Inheritance，每个Array，Function等都会遇到对象，作为每件事物的父母/终极父母

a = [];
b = function(){}
a instanceof Object // true
b instanceof Object // true

Answer 3

在Javascript中，所有本机函数都从基类Object继承。所以所有对象都是Object的实例。

Check Array，String，都是Object的实例。

javascript中必须知道的事实。

can对象是多种类型的实例？

3 个答案: