汚染されるメソッドとされないメソッド

by rough cheap

JavaScript

var Person = function(name, age) {
	var greeting = "Hello!!!";
	if (!(this instanceof Person)) {
  	return new Person(name, age);
  }
	this.name = name;
  this.age = age;
  
  this.sayHello = function() {
  	return greeting + " My name is " + this.name + ", " + this.age + " years old.";
  }
}

Person.prototype.sayHello = function() {
	return "My name is" + this.name + ".";
}

var taro = new Person("taro", 20);

Person.prototype.sayHello = function() {
	return "My name is " + this.name + ", " + this.age + " years old.";
}

alert(taro.sayHello());