Comment the scary regexp.

.internal/stringToPath.js

@@ -2,7 +2,20 @@ import memoizeCapped from './memoizeCapped.js'
 
 /** Used to match property names within property paths. */
 const reLeadingDot = /^\./
-const rePropName = /[^.[\]]+|\[(?:(-?\d+(?:\.\d+)?)|(["'])((?:(?!\2)[^\\]|\\.)*?)\2)\]|(?=(?:\.|\[\])(?:\.|\[\]|$))/g
+
+const rePropName = RegExp([
+  // Match anything that isn't a dot or bracket.
+  '[^.[\\]]+',
+  // Or match property names within brackets.
+  '\\[(?:' +
+    // Match numbers.
+    '(-?\\d+(?:\\.\\d+)?)' + '|' +
+    // Or match strings (supports escaping quotation marks).
+    '(["\'])((?:(?!\\2)[^\\\\]|\\\\.)*?)\\2' +
+  ')\\]',
+  // Or match "" as the space between consecutive dots or empty brackets.
+  '(?=(?:\\.|\\[\\])(?:\\.|\\[\\]|$))'
+].join('|'), 'g')
 
 /** Used to match backslashes in property paths. */
 const reEscapeChar = /\\(\\)?/g