statics.js

/** Constructor Functions **/
function Person(name){
  this.name=name;
}
Person.isNamed=function(instance){return !!instance.name}

var you=new Person(); /** @returns 
                          Person { name: undefined
                                 __proto__: constructor: ƒ Person{
                                                                    isNamed: ƒ (instance)
                                                                }  
                                  } 
                       **/                         
Person.isNamed(you); //@returns false;

/** class Constructor **/
class Person{

constructor(name){
  this.name=name;
  }
static isNamed(instance){
      return !!instance.name;
  }
}