Scope safe constructors

Our goal is to identify when the constructor was called without the new operator and then invoke the constructor properly. Observe the following code.

function CarPart(name) {
  if(this instanceof CarPart) { = name;
  } else {
    return new CarPart(name);

In this code, we evaluate if the this object is a CarPart and proceed as normal. If the this object is not a CarPart (ie, it's a window object), call the constructor again, this time with the new operator.

Now our constructor works properly with or without the new operator.