Determining the size of a component

As an Om neophyte, you might be wondering what the difference is between building subcomponents and just regular functions that return HTML. Let's look at a hypothetical choice borrowed from our previous todo list example:

(defn todo-item [cursor owner] 
  (dom/div nil 
    (dom/span #js {:className (when (:done? cursor) 
                                "done")} 
      (:text )))))cursor)))) 
  
(defn todo-list  [cursor owner] 
  (reify om/IRender 
    (render [_] 
      (dom/div nil 
        (dom/h1 nil (:text cursor))  
        (dom/div nil 
                       (for [t (:todos cursor)] 
                          (todo-item t owner))))))) ``` 

This is a slightly modified version of our previous todo application. Here, todo-item is a standard function that happens to return virtual DOM nodes rather than an Om component constructor. It doesn't call reify. The todo-list calls the function...