refactors Discourse.debounce

app/assets/javascripts/discourse/components/debounce.js

@@ -1,6 +1,7 @@
 /**
   Debounce a Javascript function. This means if it's called many times in a time limit it
-  should only be executed once.
+  should only be executed once (at the end of the limit counted from the last call made).
+  Original function will be called with the context and arguments from the last call made.
 
   @method debounce
   @module Discourse
@@ -8,32 +9,16 @@
   @param {Number} wait how long to wait
 **/
 Discourse.debounce = function(func, wait) {
-  var timeout = null;
+  var self, args;
+  var later = function() {
+    func.apply(self, args);
+  };
 
   return function() {
-    var context = this;
+    self = this;
-    var args = arguments;
+    args = arguments;
 
-    var later = function() {
+    Ember.run.debounce(null, later, wait);
-      timeout = null;
-      return func.apply(context, args);
-    };
-
-    if (timeout) return;
-
-    var currentWait;
-    if (typeof wait === "function") {
-      currentWait = wait();
-    } else {
-      currentWait = wait;
-    }
-
-    if (timeout) {
-      clearTimeout(timeout);
-    }
-
-    timeout = setTimeout(later, currentWait);
-    return timeout;
   };
 };
 

test/javascripts/components/debounce_test.js

@@ -4,6 +4,10 @@ var firedOnce = function(message) {
   ok(original.calledOnce, message);
 };
 
+var firedTwice = function(message) {
+  ok(original.calledTwice, message);
+};
+
 var notFired = function(message) {
   ok(!original.called, message);
 };
@@ -39,27 +43,20 @@ test("executes delayed function only once, no matter how many times debounced fu
   firedOnce("second call was supressed");
 });
 
-test("does not prolong the timeout when the debounced function is called for the second time during the timeout", function() {
+test("prolongs the timeout when the debounced function is called for the second time during the timeout", function() {
   debounced();
 
   clock.tick(50);
   debounced();
 
   clock.tick(50);
-  firedOnce("function is executed exactly at the end of the original timeout");
+  notFired("at the end of the original timeout nothing happens");
-});
-
-test("returns a JS timer handle that allows delayed execution to be cancelled before the timeout ends", function() {
-  var timerId = debounced();
 
   clock.tick(50);
-  clearTimeout(timerId);
+  firedOnce("function is executed exactly at the end of the prolonged timeout");
-
-  clock.tick(50);
-  notFired("timeout has ended but function was not executed");
 });
 
-test("preserves first call's context and params when executing delayed function", function() {
+test("preserves last call's context and params when executing delayed function", function() {
   var firstObj = {};
   var secondObj = {};
 
@@ -67,11 +64,11 @@ test("preserves first call's context and params when executing delayed function"
   debounced.call(secondObj, "second");
 
   clock.tick(100);
-  ok(original.calledOn(firstObj), "the context of the first of two subsequent calls is preserved");
+  ok(original.calledOn(secondObj), "the context of the last of two subsequent calls is preserved");
-  ok(original.calledWithExactly("first"), "param passed during the first of two subsequent calls is preserved");
+  ok(original.calledWithExactly("second"), "param passed during the last of two subsequent calls is preserved");
 });
 
-test("can be called again (with a different context and params) after timeout passes", function() {
+test("can be called again after timeout passes", function() {
   var firstObj = {};
   var secondObj = {};
 
@@ -81,6 +78,5 @@ test("can be called again (with a different context and params) after timeout pa
   debounced.call(secondObj, "second");
 
   clock.tick(100);
-  ok(original.calledOn(secondObj), "function is executed with the context of the call made after the timeout has passed");
+  firedTwice();
-  ok(original.calledWithExactly("second"), "function is executed with the param passed to the call made after the timeout has passed");
 });