Passing null or undefined fails without a helpful error

[DominicSherman]

Might not want to allow it, but if so should update the type definition to explicitly disallow it or throw a more helpful error

[andrewmclagan]

I think the issue comes from the fact that undefined properties of objects are still properties of the object:

if(o.myProperty === undefined) {
  alert("myProperty value is the special value `undefined`");
}

// versus...

if(!o.hasOwnProperty('myProperty')) {
  alert("myProperty does not exist");
}