<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Dogadd2</title> <script> function Dog(name, breed, weight){ this.name = name; this.breed = breed; this.weight = weight; } Dog.prototype.species = "Canine"; Dog.prototype.bark = function(){ if (this.weight > 25){ console.log(this.name + " Woof"); } }; var fido = new Dog("fido", "mixed", 38); fido.bark(); Dog.prototype.sitting = false; Dog.prototype.sit = function(){ if (this.sitting){ console.log(this.name + " is already sitting"); } else { this.sitting = true; console.log(this.name + " is start sitting"); } }; //hasOwnProperty,如果属性是在实例中定义的返回true，如果是在圆型定义返回false var barnaby = new Dog("Barnaby", "Basset Hound", 55); console.log(barnaby.hasOwnProperty("sitting")); barnaby.sit(); console.log(barnaby.hasOwnProperty("sitting")); console.log(fido.hasOwnProperty("sitting")); fido.sit(); console.log(fido.hasOwnProperty("sitting")); </script> </head> <body> </body> </html>