javascript - 是否可以将对象计为 "whole"？

Question

我可以数一个物体吗？喜欢:

 var student1 = new Student();
student1.name("ziv");
student1.age();
student1.where("a");


 var student2 = new Student();
student2.name("dani");
student2.age();
student2.where("b");

 var student3 = new Student();
student3.name("bari");
student3.age();
student3.where("c");

一些函数会计算它们并返回 3 。

谢谢:)

Answer 1

我想你的意思是计算实例。您必须跟踪实例，例如使用数组

var students = [];
var student1 = new Student()
   ,student2 = new Student();
students.push(students1,students2);
/* later ... */
var nOfStudents = students.length; //=> 2

另一个想法是向 Student 原型(prototype)添加一个计数器:

Student.prototype.instanceCnt = 0;

并在每个实例的 Student 构造函数中递增它

   //in the Student constructor function
   function Student(){
     this.instanceCnt += 1;
     /* ... */
   }
   // usage example
   var student1 = new Student()
      ,student2 = new Student()
      ,students = student1.instanceCnt; //=> 2