All the joy of loose typing, combined with a little more strictness

tiptop-overloads.js

// Playing with overloads and stricter typing in JS -- https://github.com/cmawhorter/tiptop

var fn = require('../lib/tiptop');

function MyObj() {
  
}

MyObj.prototype.save = fn.overloaded(
  function() {
    return this.save(id);
  },

  function(id$Number) {
    return this.save(id$Number, name);
  },

  function(id$Number, name$String) {
    return this.save(id$Number, name$String, dt);
  },

  function(id$Number, name$String, dt$Date) {
    return DB_Save({
        id: id$Number
      , name: name$String
      , dt: dt$Date
    });
  }
);

// or you could also share code.  wrapped just because
(function() {
  function sharedCode() {
  
  }
  
  MyObj.prototype.blah = fn.overloaded( ... overloads that call sharedCode ... );
})()

var obj = new MyObj();
obj.save();