SOURCE

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

Parent.prototype.sayName = function() {
  console.log(this.name);
}

function Child(name, age) {
  Parent.call(this, name);  // 继承属性
  this.age = age;
}

Child.prototype = Object.create(Parent.prototype); // 通过寄生式继承继承方法
Child.prototype.constructor = Child;   // 修正构造函数指向

Child.prototype.sayAge = function() {
  console.log(this.age);
}

let child = new Child('Kevin', 25);
child.sayName();  // Kevin 
child.sayAge();   // 25