Throttle scroll event

lib/services/scroll.service.ts

@@ -2,6 +2,7 @@
 import { Injectable, EventEmitter, Output } from '@angular/core';
 import { BrowserDomAdapter } from '@angular/platform-browser/src/browser/browser_adapter';
 import { OptionsService } from './options.service';
+import { throttle } from '../utils/helpers';
 
 export const INVIEW_POSITION = {
   ABOVE : 1,
@@ -60,7 +61,8 @@ export class ScrollService {
 
   bind() {
     this.prevOffsetY = this.scrollY();
-    this._cancel = this.dom.onAndCancel(this.$scrollParent, 'scroll', (evt) => { this.scrollHandler(evt); });
+    this._cancel = this.dom.onAndCancel(this.$scrollParent, 'scroll',
+      throttle((evt) => { this.scrollHandler(evt); }, 100, this));
   }
 
   unbind() {

lib/utils/helpers.ts

@@ -89,3 +89,27 @@ export function safePush(obj, prop, val) {
   if (!obj[prop]) obj[prop] = [];
   obj[prop].push(val);
 }
+
+// credits https://remysharp.com/2010/07/21/throttling-function-calls
+export function throttle(fn, threshhold, scope) {
+  threshhold = threshhold || 250;
+  var last,
+      deferTimer;
+  return function () {
+    var context = scope || this;
+
+    var now = +new Date,
+        args = arguments;
+    if (last && now < last + threshhold) {
+      // hold on to it
+      clearTimeout(deferTimer);
+      deferTimer = setTimeout(function () {
+        last = now;
+        fn.apply(context, args);
+      }, threshhold);
+    } else {
+      last = now;
+      fn.apply(context, args);
+    }
+  };
+}