has own property javascript es6 code example

Example 1: how reliable is js hasownproperty

o = new Object();
o.propOne = null;
o.hasOwnProperty('propOne');   // returns true
o.propTwo = undefined;  
o.hasOwnProperty('propTwo');   // returns true

Example 2: hasOwnProperty.call js

var foo = {
  hasOwnProperty: function() {
    return false;
  },
  bar: 'I belong to foo'
};