<!DOCTYPE html> <html> <head> <title></title> <meta name="viewport" content="width=device-width, initial-scale=1.0"> </head> <body> <script type="text/javascript"> /*
1.什么是instanceof关键字?
instanceof用于判断 "对象" 是否是指定构造函数的 "实例"
*/ /*
2.instanceof注意点
只要 构造函数的原型对象出现在实例对象的原型链中都会返回true
意思是person的构造函数所指向的person原型对象出现在了student的原型链中就行了
*/ /*class Person
{
name="cyg";
}
let qq=new Person();
console.log(qq instanceof Person);//qq实例是不是person构造函数所创建的实例对象
class Cat{
name = "mm";
}
let c = new Cat();
console.log(c instanceof Person);*/ function Person(myName) { this.name = myName; } function Student(myName, myScore) { Person.call(this, myName); this.score = myScore; } Student.prototype = new Person(); Student.prototype.constructor = Student; let stu = new Student(); console.log(stu instanceof Person); // true </script> </body> </html>
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