Merge pull request #1119 from mreinstein/master

add some documentation on getOffsetParent and listScrollParents

src/dom-utils/getOffsetParent.js

@@ -17,6 +17,10 @@ function getTrueOffsetParent(element: Element): ?Element {
   return element.offsetParent;
 }
 
+/*
+get the closest ancestor positioned element. Handles some edge cases,
+such as table ancestors and cross browser bugs.
+*/
 export default function getOffsetParent(element: Element) {
   const window = getWindow(element);
 

src/dom-utils/listScrollParents.js

@@ -6,6 +6,12 @@ import getWindow from './getWindow';
 import type { Window, VisualViewport } from '../types';
 import isScrollParent from './isScrollParent';
 
+/*
+given a DOM element, return the list of all scroll parents, up the list of ancesors
+until we get to the top window object. This list is what we attach scroll listeners
+to, because if any of these parent elements scroll, we'll need to re-calculate the 
+reference element's position.
+*/
 export default function listScrollParents(
   element: Node,
   list: Array<Element | Window> = []