debounce.clj

(defn debounce 
  ([c ms] (debounce (chan) c ms))
  ([c' c ms]
    (go
      (loop [start nil loc (<! c)]
        (if (nil? start)
          (do
            (>! c' loc)
            (recur (js/Date.) nil))
          (let [loc (<! c)]
            (if (>= (- (js/Date.) start) ms)
              (recur nil loc)
              (recur (js/Date.) loc))))))
    c'))

debounce.js

// http://stackoverflow.com/questions/13320015/how-to-write-a-debounce-service-in-angularjs

app.factory('debounce', function($timeout, $q) {
  return function(func, wait, immediate) {
    var timeout;
    var deferred = $q.defer();
    return function() {
      var context = this, args = arguments;
      var later = function() {
        timeout = null;
        if(!immediate) {
          deferred.resolve(func.apply(context, args));
          deferred = $q.defer();
        }
      };
      var callNow = immediate && !timeout;
      if ( timeout ) {
        $timeout.cancel(timeout);
      }
      timeout = $timeout(later, wait);
      if (callNow) {
        deferred.resolve(func.apply(context,args));
        deferred = $q.defer();
      }
      return deferred.promise;
    };
  };
});

@halgari thanks for the review excellent points

I found given implementation of debounce incorrect. The point of debounce is that it gets fired exactly once after all frequent calls end. This implementation doesn't put into channel when all calls end.
This demo of debounce is correct: Ben Alman » jQuery throttle / debounce » Examples » Debounce

So I wrote bit different debounce which I think is correct

Simple version:

(defn debounce
  ([c ms] (debounce (chan) c ms))
  ([c' c ms]
   (go
     (loop [timeout nil]
       (let [loc (<! c)]
         (when timeout
           (js/clearTimeout timeout))
         (let [t (js/setTimeout #(go (>! c' loc)) ms)]
           (recur t)))))
   c'))

Version with immediate param. This should be equivalent to above AngularJS snippet. When immediate true, first call always gets fired instantly and only after that debouncing starts. It might be desired in some cases.

(defn debounce
  ([c ms] (debounce (chan) c ms false))
  ([c ms immediate] (debounce (chan) c ms immediate))
  ([c' c ms immediate]
   (go
     (loop [start (js/Date.) timeout nil]
       (let [loc (<! c)]
         (when timeout
           (js/clearTimeout timeout))
         (let [diff (- (js/Date.) start)
               delay (if (and immediate
                              (or (>= diff ms)
                                  (not timeout)))
                       0 ms)
               t (js/setTimeout #(go (>! c' loc)) delay)]
           (recur (js/Date.) t)))))
   c'))

See also https://gist.github.com/scttnlsn/9744501 for a version of debounce that outputs the final input after a flurry of inputs.