implement cancel method to throttle

angus-c · EvandroLG · Apr 18, 2021 · May 1, 2021 · May 2, 2021 · May 3, 2021
commit c487b4f6dcbfa35f60c575b5049321bf4be06534
diff --git a/packages/function-throttle/index.js b/packages/function-throttle/index.js
@@ -1,35 +1,51 @@
 module.exports = throttle;
 
 function throttle(fn, interval, options) {
-  var wait = false;
+  var timeoutId = null;
   var leading = (options && options.leading);
   var trailing = (options && options.trailing);
+
   if (leading == null) {
     leading = true; // default
   }
+
   if (trailing == null) {
     trailing = !leading; //default
   }
+
   if (leading == true) {
     trailing = false; // forced because there should be invocation per call
   }
 
-  return function() {
-    var callNow = leading && !wait;
+  var cancel = function() {
+    if (timeoutId) {
+      clearTimeout(timeoutId);
+      timeoutId = null;
+    }
+  };
+
+  var throttleWrapper = function() {
+    var callNow = leading && !timeoutId;
     var context = this;
     var args = arguments;
-    if (!wait) {
-      wait = true;
-      setTimeout(function() {
-        wait = false;
+
+    if (!timeoutId) {
+      timeoutId = setTimeout(function() {
+        timeoutId = null;
+
         if (trailing) {
           return fn.apply(context, args);
         }
       }, interval);
     }
+
     if (callNow) {
       callNow = false;
-      return fn.apply(this, arguments);
+      return fn.apply(context, args);
     }
   };
+
+  throttleWrapper.cancel = cancel;
+
+  return throttleWrapper;
 }
diff --git a/test/function-throttle/index.js b/test/function-throttle/index.js
@@ -392,3 +392,18 @@ test('invokes repeatedly when wait is falsey', function(t) {
     }, 40);
   }, 40);
 });
+
+test('cancel delayed function', function(t) {
+  t.plan(1);
+
+  var callCounter = 0;
+  var fn = throttle(function() {
+    callCounter++;
+  }, 200);
+
+  fn.cancel();
+
+  setTimeout(function() {
+    t.equal(callCounter, 0);
+  }, 400);
+});