javascript - 如何在javascript中封装数据而不在每个对象实例中重复函数？

Question

我在 JavaScript 中创建了一个具有公共(public)和私有(private)属性的类 - 数据和操作这些数据的方法。某些数据是私有(private)的，不应通过类实例中的“.”(点)运算符访问。有没有办法避免每个类实例的方法重复？

function MyClass() {
    let privateVar;
    let publicVar;
    function publicFun() {
        // do something
    }
    function privateFun(){
        // do something else
    }
    this.v = publicVar;
    this.f = publicFun;
}

let obj1 = new MyClass();
let obj2 = new MyClass();   // publicFun and privateFun methods duplication

ClassName.prototype 方法需要所有类数据的完全公共(public) API。所以这对我不起作用。

Answer 1

如果我理解正确的话，这是我的例子:

1. 方法只在包装函数中定义一次(因此它们不会在每个实例上声明)
2. 您可以创建对象的实例，它们都将引用相同的方法，并且可以公开数据。

Here是一个 fiddle 的例子:

function wrapper() {
  //Methods defined only once
  function method() {
    alert("this is method");
  }

  function methodWithParams(param, callback) {
    var paramsVar = param;

    function realMethodHere() {
      alert("We passed a param: " + paramsVar);
      paramsVar = "Changed"
      callback(paramsVar);
      alert("Now we cahnged the param's value to: " + paramsVar + ", rerun the method to verify");
    }

    return realMethodHere;
  }

  //Class constructor
  function classConstructor() {
    //Private
    var privateData = "Private"

    function privateFunction() {
      alert("this is some private function, inaccesible");
    }

    //This callback was addedto allow yo uto change private data.
    function privateDataChangerCallback(param) {
      privateData = param;
    }


    //Public
    this.publicData = "Public"
    this.callMethod = method;
    this.paramMethod = methodWithParams(privateData, privateDataChangerCallback);
  }


  return classConstructor;
}

var classDefinition = wrapper();
var classInstance = new classDefinition();

classInstance.callMethod(); //method without param
classInstance.paramMethod(); //method with exposed Private data
//rerunning the method to see what the value is:
classInstance.paramMethod(); //method with exposed Private data