In the Om Next Quick Start, they use #js and #uuid. What does the pound symbol here mean?
Link: https://github.com/omcljs/om/wiki/Quick-Start-(om.next)#components-with-queries--mutations
Snippets:
#js:
(defui Counter
static om/IQuery
(query [this]
[:count])
Object
(render [this]
(let [{:keys [count]} (om/props this)]
(dom/div nil
(dom/span nil (str "Count: " count))
(dom/button
#js {:onClick
(fn [e] (om/transact! this '[(increment)]))}
"Click me!")))))
#uuid:
(om/from-history reconciler
#uuid "9e7160a0-89cc-4482-aba1-7b894a1c54b4")
Commonly found in EDN and ClojureScript this use of # is called the tagged literal. Look at this example,
user=> (java.util.Date.)
#inst "2014-05-19T19:12:37.925-00:00"
When we create a new date it is represented as a tagged literal, or in this case a tagged string. We can use Clojures read-string to read this back (or use it directly)
user=> (type #inst "2014-05-19T19:12:37.925-00:00")
java.util.Date
(read-string "#inst \"2014-05-19T19:12:37.925-00:00\"")
#inst "2014-05-19T19:12:37.925-00:00"
user=> (type (read-string "#inst \"2014-05-19T19:12:37.925-00:00\""))
java.util.Date
A tagged literal tells the reader how to parse the literal value. Other common uses include #uuid for generating UUIDs and in the ClojureScript world an extremely common use of tagged literals is #js which can be used to convert ClojureScript data structures into JavaScript structures directly.