Performance measuring, scroll to top, array flattening

snippets/scroll-to-top.md

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+### Scroll to top
+
+Get distance from top using `document.documentElement.scrollTop` or `document.body.scrollTop`.
+Scroll by a fraction of the distance from top. Use `window.requestFrame()` to animate the scrolling.
+
+```js
+var scrollToTop = _ => {
+  var c = document.documentElement.scrollTop || document.body.scrollTop;
+  if(c > 0) {
+    window.requestAnimationFrame(scrollToTop);
+    window.scrollTo(0, c - c/8);
+  }
+}
+```