Ensure variable [scrollDir]() is used, not scrollTop(). Use Math.ab() instead of multiply by -1 if negative.

Author: koenpunt

jquery.smooth-scroll.js

@@ -1,5 +1,5 @@
 /*!
- * jQuery Smooth Scroll - v1.5.6 - 2015-09-08
+ * jQuery Smooth Scroll - v1.5.6 - 2015-12-14
  * https://github.com/kswedberg/jquery-smooth-scroll
  * Copyright (c) 2015 Karl Swedberg
  * Licensed MIT (https://github.com/kswedberg/jquery-smooth-scroll/blob/master/LICENSE-MIT)
@@ -231,12 +231,9 @@
     // automatically calculate the speed of the scroll based on distance / coefficient
     if (speed === 'auto') {
 
-      // $scroller.scrollTop() is position before scroll, aniProps[scrollDir] is position after
+      // $scroller[scrollDir]() is position before scroll, aniProps[scrollDir] is position after
       // When delta is greater, speed will be greater.
-      delta = aniProps[scrollDir] - $scroller.scrollTop();
-      if(delta < 0) {
-        delta *= -1;
-      }
+      delta = Math.abs(aniProps[scrollDir] - $scroller[scrollDir]());
 
       // Divide the delta by the coefficient
       speed = delta / opts.autoCoefficient;

jquery.smooth-scroll.min.js

@@ -30,7 +30,7 @@
     "grunt": "~0.4.0",
     "grunt-contrib-concat": "~0.5.0",
     "grunt-contrib-jshint": "~0.1.1",
-    "grunt-contrib-uglify": "~0.1.1",
+    "grunt-contrib-uglify": "~0.2.0",
     "grunt-contrib-watch": "~0.3.1",
     "grunt-shell": "~0.2",
     "grunt-version": "~0.1.1",

package.json

@@ -212,12 +212,9 @@
     // automatically calculate the speed of the scroll based on distance / coefficient
     if (speed === 'auto') {
 
-      // $scroller.scrollTop() is position before scroll, aniProps[scrollDir] is position after
+      // $scroller[scrollDir]() is position before scroll, aniProps[scrollDir] is position after
       // When delta is greater, speed will be greater.
-      delta = aniProps[scrollDir] - $scroller.scrollTop();
-      if(delta < 0) {
-        delta *= -1;
-      }
+      delta = Math.abs(aniProps[scrollDir] - $scroller[scrollDir]());
 
       // Divide the delta by the coefficient
       speed = delta / opts.autoCoefficient;