How to create privacy using bind ()

Question

I pass the object literal to a structure method called supportP() . This object literal has the special property _p , which means that its members are private. From with in an object literal can be obtained through this._p . However, when I pass the object literal to the "external" volume, I do not copy _p . Now it was closed by inaction. To access _p from public member methods, I bind them to the original object using bind() so that they still have access to _p through this .

Will this work? Are there any other questions? Some feedback is required before I checked it.

Below are the relevant snippets.

 /*$A.supportP ** ** ** */ $A.supportP = function (o, not_singleton) { var oo key; SupportList[o.Name] = {}; if (not_singleton) { // ignore this section } else { // *look here - isFunc returns true if a function for (key in o) { if ((key !== '_p') && (isFunc(o[key])) { oo[key] = o[key].bind(o); } else if (key !== '_p') { oo[key] = o[key]; } else { // private (_p) - anything to do here? } } return oo; } }; /*$A.test ** ** ** */ var singleton_object = $A.supportP({ _p: 'I am private', Name: 'test', publik_func: function () { // this will refer to this object so that it can access _p // this._p is accessible here due to binding } }, false); 

Answer 1

Will this work?

Yes, you can access the "private" property through this._p .

Are there any other questions?

You are cloning an object. However, the method on it does not have access to it - it is tied to the "old" object, whose properties do not reflect changes in the copy. I'm not sure if this is by design or by accident.

---

For strict privacy, you will need to use closures with local variables. Properties can never be closed.

 var singleton_object = (function() { var _p = 'I am private'; // local variable return { Name: 'test', publik_func: function () { // this will refer to this object so that it can access the properties // _p is accessible here due to closure, but not to anything else } }; }()); // immediately-executed function expression 

---

Another solution using two different objects (one hidden) that are passed to the structure method:

 function bindPrivates(private, obj) { for (var key in obj) if (typeof obj[key] == "function") obj[key] = obj[key].bind(obj, private); return obj; } var singleton_object = bindPrivates({ p: 'I am private' }, { Name: 'test', publik_func: function (_) { // this will refer to this object so that it can access "public" properties // _.p, a "private property" is accessible here due to binding the private // object to the first argument } });