私有

function foo() {
  var a = 5;
  return {
    getA:function() {return a}
  }
 
}
foo().getA

function Foo() {
  var a = 5;
  var b = 6;
  this.getName = function() {
   return a+b
  }
}
undefined
var foo = new Foo()
undefined
foo.getName()
11