Force a constructor method if 'new' isn't used.

force_constructor.js

function Podcast(title, url) {
    // Forces the new instance so that 'this' has context inside Podcast
    if(false === (this instanceof Podcast)) {
        return new Podcast(title, url);
    }
  
    this.title = title;
    this.url = url;
    
    this.toString = function() {
      return 'Title: ' + this.title;
    }
}

var podcast1 = new Podcast('Astronomy cast', 'http:// ...');
var podcast2 = Podcast('jQuery podcast', 'http:// ...');

console.log(podcast1, podcast2);