feat(progress): add throttle for progress events;

lib/helpers/AxiosTransformStream.js

@@ -78,7 +78,7 @@ class AxiosTransformStream extends stream.Transform{
     }, internals.ticksRate);
 
     const onFinish = () => {
-      internals.updateProgress(true);
+      internals.updateProgress.call(true);
     };
 
     this.once('end', onFinish);

lib/helpers/progressEventReducer.js

@@ -1,10 +1,11 @@
 import speedometer from "./speedometer.js";
+import throttle from "./throttle.js";
 
-export default (listener, isDownloadStream) => {
+export default (listener, isDownloadStream, freq = 3) => {
   let bytesNotified = 0;
   const _speedometer = speedometer(50, 250);
 
-  return e => {
+  return throttle(e => {
     const loaded = e.loaded;
     const total = e.lengthComputable ? e.total : undefined;
     const progressBytes = loaded - bytesNotified;
@@ -27,5 +28,5 @@ export default (listener, isDownloadStream) => {
     data[isDownloadStream ? 'download' : 'upload'] = true;
 
     listener(data);
-  };
+  }, freq);
 }

lib/helpers/throttle.js

@@ -10,21 +10,23 @@ function throttle(fn, freq) {
   let timestamp = 0;
   const threshold = 1000 / freq;
   let timer = null;
-  return function throttled(force, args) {
+  return function throttled() {
+    const force = this === true;
+
     const now = Date.now();
     if (force || now - timestamp > threshold) {
       if (timer) {
         clearTimeout(timer);
         timer = null;
       }
       timestamp = now;
-      return fn.apply(null, args);
+      return fn.apply(null, arguments);
     }
     if (!timer) {
       timer = setTimeout(() => {
         timer = null;
         timestamp = Date.now();
-        return fn.apply(null, args);
+        return fn.apply(null, arguments);
       }, threshold - (now - timestamp));
     }
   };