Question

I’m using the revealing module pattern somewhat like this:

var SomeClosure = function () {

  var SomeInnerVar = 4;

  function InnerGetTheVar() {
     return SomeInnerVar;
  } 

  function InitClosure() {
       // there's something else happening here that requires me to 
       // wait for document.ready before initializing the closure
       setInterval(IncreaseSomeInnerVar, 10000);
  }

  function IncreaseSomeInnerVar() {
     SomeInnerVar = SomeInnerVar  + 1;
  }

  InitClosure();

  return  {
     GetTheVar: InnerGetTheVar
  }
}

$(document).ready(function () {

   SomeClosure = SomeClosure();
}); 

Now why is it that if in the console I type this:

SomeClosure.GetTheVar = 2;
SomeClosure.GetTheVar; // outputs 2!

Why doesn’t the closure keep SomeInnerVar protected? I don’t want the outer scope to be able to change SomeInnerVar like that.

Thanks for your suggestions.

Answer 1

Instead of just returning an object literal, use Object.defineProperty:

var out = {};

if ( Object.defineProperty ) {
    Object.defineProperty(out, 'GetTheVar', {
        value: InnerGetTheVar,
        writable: false
    });
} else {
    out.GetTheVar = InnerGetTheVar;
}

return out;