v4.0.2

* Combines existing history state on in-page navigation
* Avoids errors on old browsers (e.g., IE9) that don’t support
history.pushState() and history.replaceState()

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "zenscroll",
-	"version": "4.0.1",
+	"version": "4.0.2",
 	"description": "A module to smooth-scroll web pages and scrollable elements (like DIVs)",
 	"main": "zenscroll.js",
 	"files": ["zenscroll.js", "zenscroll-min.js"],

zenscroll.js

@@ -1,5 +1,5 @@
 /**
- * Zenscroll 4.0.1
+ * Zenscroll 4.0.2
  * https://github.com/zengabor/zenscroll/
  *
  * Copyright 2015–2018 Gabor Lenard
@@ -258,8 +258,8 @@
 	// Exclude IE8- or when native is enabled or Zenscroll auto- is disabled
 	if ("addEventListener" in window && !window.noZensmooth && !isNativeSmoothScrollEnabledOn(document.body)) {
 
-
-		var isScrollRestorationSupported = "scrollRestoration" in history
+		var isHistorySupported = "history" in window && "pushState" in history
+		var isScrollRestorationSupported = isHistorySupported && "scrollRestoration" in history
 
 		// On first load & refresh make sure the browser restores the position first
 		if (isScrollRestorationSupported) {
@@ -313,8 +313,10 @@
 			}
 			// Save the current scrolling position so it can be used for scroll restoration:
 			if (isScrollRestorationSupported) {
+				var historyState = history.state && typeof history.state === "object" ? history.state : {}
+				historyState.zenscrollY = zenscroll.getY()
 				try {
-					history.replaceState({ zenscrollY: zenscroll.getY() }, "")
+					history.replaceState(historyState, "")
 				} catch (e) {
 					// Avoid the Chrome Security exception on file protocol, e.g., file://index.html
 				}
@@ -338,7 +340,9 @@
 				var edgeOffset = zenscroll.setup().edgeOffset
 				if (edgeOffset) {
 					targetY = Math.max(0, targetY - edgeOffset)
-					onDone = function () { history.pushState(null, "", href) }
+					if (isHistorySupported) {
+						onDone = function () { history.pushState({}, "", href) }
+					}
 				}
 				zenscroll.toY(targetY, null, onDone)
 			}