prototype3.js

// class A
function ParentA(a) {
  this.a = a;
};
ParentA.prototype.displayA = function () {
  console.log('a: %s', this.a);
}

// class B
function ParentB(b) {
  this.b = b;
};
ParentB.prototype.displayB = function () {
  console.log('b: %s', this.b);
}

// Child 继承于 ParentA 和 ParentB

function Child(a, b) {
  // inherits from A and B
// ParentA.apply(this, [a])
// ParentB.apply(this, [b])
  ParentA.call(this, a)
  ParentB.call(this, b)
};

Child.prototype = Object.create(ParentA.prototype)
//Child.prototype = Object.create(ParentB.prototype)
// 把 ParentB.prototype 上的东西 copy 过来
//手动吗
//en
for(var method in ParentB.prototype){
  Child.prototype[method] = ParentB.prototype[method]
}

Child.prototype.displayAB = function(){
  console.log('a: %s', this.a);
  console.log('b: %s', this.b);
}

Child.prototype.constructor = Child

var child = new Child('a', 'b');

console.log(child)
console.log(child.__proto__)

console.log(child.a); // a
console.log(child.b); // b
console.log(child.__proto__.constructor === Child) // true
child.displayA(); // a: a
child.displayB();// b: b
child.displayAB();// a: a, b: b