Default properties without using external libraries using prototype inheritance

default.js

function MyConstructor(options){
  options = options || {};
  // Default properties:
  options.__proto__ = {
    threshold: 3,
    quality: 1
    etc: "whatever"
  };
  
  // Use case:
  this.render = new MyDummyRenderer(options.quality);
}

// Calling the constructor can be as easy as:
var myConstructorInstance = new MyConstructor();
// And you are able to call properties like:
myConstructorIntance.render;