gistfile1.js

var SomeClass = function() {
  // constructor
}

copyProperties(SomeClass, {
  staticMethodA: function() {

  }
})

copyProperties(SomeClass.prototype, {
  methodA: function() {

  },
  // ...
});

class SomeClass {
  constructor() {

  }

  static staticMethodA() {

  }

  methodA() {
    
  }
}