initialize: function(options) {
if (options) {
this.options = {};
this.options.container = options.container || ‘container’;
this.options.selector = options.selector || ‘a’;
/* any other option */
},

I did it till now, when I searched about your way to make initialization. The good part is that with prototype you can use Object#extend to copy all the properties from one object to another. So we can have

initialize: function(options) {
this.options = Object.extend({
container: ‘container’,
selector: ‘a’
/* any other option */
}, options || {});
},

In this way the code became much more readable, because you *firstly* set all the default options, and then you change them just using the arguments.