原型函数与javascript中的普通函数有何不同？

function Person(name) {
  this.name = name;
}

// 原型函数
Person.prototype.sayHello = function() {
  console.log('Hello, my name is ' + this.name);
}

// 普通函数
Person.prototype.sayGoodbye = function() {
  console.log('Goodbye, my name is ' + this.name);
}

var person1 = new Person('John');
person1.sayHello(); // 输出 "Hello, my name is John"
person1.sayGoodbye(); // 输出 "Goodbye, my name is John"