使用prototype属性来减少重复的代码
function Dog(name){
this.name=name;
}
let beagle=new Dog;
Dog.prototype.numLegs = 4;
console.log(beagle.numLegs);
function Dog(name){
this.name=name;
}
let beagle=new Dog;
Dog.prototype.numLegs = 4;
console.log(beagle.numLegs);