UI Selectable: pass values of <td> id's to hidden input

UI Selectable: pass values of <td> id's to hidden input

Hello, 

rdworth posted an example of how to use UI Selectable 
in conjunction with a table. 

I'm having trouble passing the <td> id's to an input, though. 

The jsbin example below only partially works, 
but the goal here is to pass the <td> #id 
with no comma at the end of the string. 



Thoughts?...