From f22ae1ba545a10e826960a6af13143c6d4c79346 Mon Sep 17 00:00:00 2001
From: SleepWalker <mybox@udf.su>
Date: Sat, 4 Jun 2016 10:26:54 +0300
Subject: [PATCH] #131: easing for scroll animation

---
 src/components/ui/scrollTo.js | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/components/ui/scrollTo.js b/src/components/ui/scrollTo.js
index dbcdbf5..e95ed23 100644
--- a/src/components/ui/scrollTo.js
+++ b/src/components/ui/scrollTo.js
@@ -1,28 +1,30 @@
 /**
  * Implements scroll to animation with momentum effect
+ *
+ * @see http://ariya.ofilabs.com/2013/11/javascript-kinetic-scrolling-part-2.html
  */
 
 const requestAnimationFrame = window.requestAnimationFrame || window.mozRequestAnimationFrame
     || window.webkitRequestAnimationFrame || window.msRequestAnimationFrame;
 
-const DURATION = 500;
+const TIME_CONSTANT = 100;
 export default function scrollTo(y) {
     const start = Date.now();
     const {scrollTop} = document.body;
-    const delta = y - scrollTop;
+    const amplitude = y - scrollTop;
 
     requestAnimationFrame(function animateScroll() {
         const elapsed = Date.now() - start;
 
-        let interpolatedY = scrollTop + delta * (elapsed / DURATION);
+        let delta = -amplitude * Math.exp(-elapsed / TIME_CONSTANT);
 
-        if (interpolatedY < y) {
+        if (Math.abs(delta) > 0.5) {
             requestAnimationFrame(animateScroll);
         } else {
-            interpolatedY = y;
+            delta = 0;
         }
 
-        window.scrollTo(0, interpolatedY);
+        window.scrollTo(0, y + delta);
     });
 }