Entangled function

test.js

var e = (()=>{
  var c = 0;
  return {
    a : ()=>c,
    b : (x)=>{c=x;}
  };
})();
var a = e.a;
var b = e.b;
console.log(a()); // => 0
b(4);
console.log(a()); // => 4