Chaining promises in ClojureScript is best done using the thread-first macro, ->. Here's an example of using the fetch API:
(-> (js/fetch "/data")
(.then (fn [r]
(when-not (.-ok r)
(throw (js/Error. "Could not fetch /data")))
(.json r)))
Short write up on using REPL when developing UIs in ClojureScript.
Everyone's standard approach to hot-reloading is to use a tool (Figwheel or shadow-cljs) that reloads changed namespaces automatically. This works really well: you change the code, the tool picks up changed files, compiles namespaces and dependants, notifies REPL client which then pulls in compiled changes, and re-runs a function that re-renders UI.
The other approach is to use ClojureScript's REPL directly and rely only on eval from the editor. This more or less matches Clojure style workflow. This approach might be useful when you don't want tools overhead or hot-reloading becomes slow for you or you just used to this style of interactions. Also changing code doesn't always mean that you want to reload all the changes. On the other hand it is very easy to change a couple of top-level forms and forget to eval one of them.
| // returns the value in a nested associative structure, | |
| // just like (get-in) in clojure | |
| var getIn = function (obj, path) { | |
| if (!_(path).isArray()) // normalize | |
| path = _(arguments).toArray().rest().value(); | |
| if (path.length === 0) | |
| return obj; | |
| if (!_(obj).has(_.first(path))) |
| (ns n01se.externs-for-cljs | |
| (:require [clojure.java.io :as io] | |
| [cljs.compiler :as comp] | |
| [cljs.analyzer :as ana])) | |
| (defn read-file [file] | |
| (let [eof (Object.)] | |
| (with-open [stream (clojure.lang.LineNumberingPushbackReader. (io/reader file))] | |
| (vec (take-while #(not= % eof) | |
| (repeatedly #(read stream false eof))))))) |
