since you are passing the selector `"[data-toggle='post-preview']"` as a parameter to the init function, you might want to go ahead and remove a reference to 'post-preview' on line 11
Instead of "[data-toggle='post-preview']" as a parameter, you could use `'post-preview'` and infer all selector from there 
The same also on line 39 or 54. That code would be then completely independent from post-preview and could be used again theoretically for another kind of preview.
Makes sense?