javascript - javascript中从一个实例继承

Question

我想知道是否可以有这样的东西:

• 基础类A
• 从A类的一个实例a派生类B1(即a = new A())
• 从A的同一实例a派生类B2

我举个例子:

var a = new A();
function A() {
    this.var_test = 0;
    this.test = function () {
        alert(this.var_test++);
    }
}

function B1() {
}
B1.prototype = a;

function B2() {         
}
B2.prototype = a;

var b1 = new B1();
var b2 = new B2();
b1.test(); // i want alert(0)
b2.test(); // i want alert(1)

怎么做？

Answer 1

Sure, just use the standard methods for inheritance :

console.clear();
function A() {
  this.test = function() {
    alert(A.var_test++);
  }
  A.var_test = 0;
}
var a = new A();
b1 = Object.create(a);
b2 = Object.create(a);
b1.test();
b2.test();
b1.test();
b2.test();