Safe constructor.

safe-constructor.js

var Constructor = function() {
  if (!(this instanceof Constructor)) {
    return new Constructor();
  }
  
  // Properties and methods...
  this.something = 'something';
  
  // ...
}

var object1 = new Constructor(),
    object2 = Constructor();

console.log(object1.something); // 'something'
console.log(object2.something); // 'something'