Nice looking JQuery with Clojurescript

I did a bit of frontend work for internal tools recently and chose to go with clojurescript, for obvious reasons.

Like clojure, clojurescript supports macros which let you express common lengthy idioms. I use the jayq library to interact with the browser since JQuery is the de-facto standard and battle tested.

A standard call to a JSON get in JQuery looks like this:

$.getJSON('ajax/test.json', function(data) {

Which is really a call to:

  url: 'ajax/test.json',
  dataType: 'json',
  success: function(data) { doSomethingWith(data); }

Now when using jayq this would translate to:

(ajax "ajax/test.json"
      {:dataType "json"
       :success  (fn [data] (do-something-with data))})

This is just as simple, but a bit lacking in terms of readability, with a simple, add to this that you might want to check the done status of the resulting future and you end up with:

(let [ftr (ajax "ajax/test.json"
                {:dataType "json"
                 :success  (fn [data] (do-something-with data))})]
  (.done ftr (fn [] (refresh-view))))

Thankfully, with macros we can make this much prettier, with these two simple macros:

(defmacro when-done
  [ftr & body]
  `(.done ~ftr (fn [] ~@body)))

(defmacro with-json
  [sym url & body]
    {:dataType "json"
     :success  (fn [data#] (let [~sym (cljs.core/js->clj data#)] ~@body))}))

We can now write:

(when-done (with-json data "ajax/test.json" (do-something-with data))

Which clearly turns down the suck on the overall aspect of your callback code.

There’s a lot more to consider of course, as evidenced by this PR, but it’s a good showcase of clojurescript’s abilities.