javascript - 对除 JavaScript 中的一个对象之外的所有对象隐藏对象属性

Question

假设我有代码:

function Obj(){
  var _x = 5;
  this.getX = function(){
    return _x;
  };
}

var obj = new Obj();

function God(){
  var x = obj.getX(); // i want 5 here
}

function Human(){
  var x = obj.getX(); // i want error/undefined here
}

var x = obj.getX(); // i want error/undefined here too

如何对除一个对象之外的所有对象隐藏 getX 属性？

Answer 1

假设您通过 new God 和 new Human 使用 God 和 Human 作为对象，您可以使用锁和 key 来允许以正确的类型访问该函数:

function Obj(lock) {
    var _x = 5;
    this.getX = function (key) {
        if (key instanceof lock) {
            return _x;
        }
    };
}

function God() {
    var x = obj.getX(this);
    console.log(x);
}

function Human() {
    var x = obj.getX(this);
    console.log(x);
}

var obj = new Obj(God);
var g = new God();   // logs 5
var h = new Human(); // logs undefined

当然，人们总是可以 pry 锁:

function Thief() {
    var g = new God();
    var x = obj.getX(g);
}

var t = new Thief(); // logs 5

<小时/>

这种锁和 key 机制的另一种方法是通过共享 secret :

function Obj(lock) {
    var _x = 5;
    this.getX = function (key) {
        if (lock === key) {
            return _x;
        }
    };
}

(function (scope) {
    //When I wrote this, only God and I understood what I was doing
    //Now, God only knows
    var secret = {};
    scope.God = function () {
        var x = scope.obj.getX(secret);
        console.log(x);
    };
    scope.obj = new Obj(secret);
}(window));

function Human() {
    var x = obj.getX();
    console.log(x);
}

var g = new God();
var h = new Human();