delay loading of EventSource and WebSocket

[loomis]

Delay the loading of EventSource and WebSocket until they are used. This allows kvlt to be used on browsers that don't support them as long as the features are not actually used.

[loomis]

Related to #20 and #25.

[moea]

@loomis: Thanks!

Because the single arg constructor calls are the only two times those defines are used, maybe this might be cleaner than the let?

(def eventsource (delay (js/require "eventsource")))

(defn event-source [url]
  (if (exists? js/EventSource)
    (js/EventSource. url)
    (try
     (@eventsource. url)
     (catch js/Error e
       ...))))

at least with recent clojurescript builds, this works:

cljs.user> (def x (delay js/Object))
#'cljs.user/x
cljs.user> (@x.)
#js {}

but if it doesn't, generally, then confining the local binding to that function might be cleaner.

If that's a pain for you, I can merge this into a branch and take care of it.

[loomis]

@moea No problem. I'll refactor the PR and retest.

[moea]

@loomis This looks good to me, I'll merge and push an updated 0.2.0-SNAPSHOT after updating the promesa dep.

[loomis]

@moea Thanks for the feedback. I've refactored the PR. This is working for me and the standard tests pass now. You'll notice that the only change between the last two commits was switching from:

(@websocket-node. url)

which fails the unit test to

(let [ws @websocket-node]
  (ws. url)

which passes. I don't pretend to understand why the first works fine from the repl, but fails when compiled.

[moea]

0.1.5-SNAPSHOT, rather, as there are no breaking changes in this branch. Just released to clojars.