From e9b1ceca2345face362f8d88f4c34b6e03548ed6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Philippe=20Rivi=C3=A8re?= <fil@rezo.net>
Date: Mon, 4 Dec 2023 12:12:09 +0100
Subject: [PATCH 1/4] save sidebar scrolltop on beforeunload restore on load

closes #305
---
 src/render.ts | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/render.ts b/src/render.ts
index f6d0bffe4..2727efb4b 100644
--- a/src/render.ts
+++ b/src/render.ts
@@ -138,6 +138,9 @@ function renderSidebar(title = "Home", pages: (Page | Section)[], path: string):
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
+  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
+  if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>`;
 }
 

From 630bc703d304c119f50f3ccc8f1e85b30e23aafe Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Philippe=20Rivi=C3=A8re?= <fil@rezo.net>
Date: Mon, 4 Dec 2023 12:12:21 +0100
Subject: [PATCH 2/4] fix tests

---
 test/output/build/archives/tar.html              | 3 +++
 test/output/build/archives/zip.html              | 3 +++
 test/output/build/config/closed/page.html        | 3 +++
 test/output/build/config/index.html              | 3 +++
 test/output/build/config/one.html                | 3 +++
 test/output/build/config/sub/two.html            | 3 +++
 test/output/build/config/toc-override.html       | 3 +++
 test/output/build/config/toc.html                | 3 +++
 test/output/build/fetches/foo.html               | 3 +++
 test/output/build/fetches/top.html               | 3 +++
 test/output/build/files/files.html               | 3 +++
 test/output/build/files/subsection/subfiles.html | 3 +++
 test/output/build/imports/foo/foo.html           | 3 +++
 test/output/build/missing-file/index.html        | 3 +++
 test/output/build/missing-import/index.html      | 3 +++
 test/output/build/multi/index.html               | 3 +++
 test/output/build/multi/subsection/index.html    | 3 +++
 test/output/build/simple-public/index.html       | 3 +++
 test/output/build/simple/simple.html             | 3 +++
 test/output/build/subtitle/index.html            | 3 +++
 20 files changed, 60 insertions(+)

diff --git a/test/output/build/archives/tar.html b/test/output/build/archives/tar.html
index 0c1bf3e2a..9f6c8a885 100644
--- a/test/output/build/archives/tar.html
+++ b/test/output/build/archives/tar.html
@@ -76,6 +76,9 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
+  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
+  if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
 <div id="observablehq-center">
 <main id="observablehq-main" class="observablehq">
diff --git a/test/output/build/archives/zip.html b/test/output/build/archives/zip.html
index 75552f62b..9a34b9c03 100644
--- a/test/output/build/archives/zip.html
+++ b/test/output/build/archives/zip.html
@@ -62,6 +62,9 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
+  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
+  if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
 <div id="observablehq-center">
 <main id="observablehq-main" class="observablehq">
diff --git a/test/output/build/config/closed/page.html b/test/output/build/config/closed/page.html
index 2faa66baa..82577a191 100644
--- a/test/output/build/config/closed/page.html
+++ b/test/output/build/config/closed/page.html
@@ -41,6 +41,9 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
+  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
+  if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
 <div id="observablehq-center">
 <main id="observablehq-main" class="observablehq">
diff --git a/test/output/build/config/index.html b/test/output/build/config/index.html
index 6b93a330b..a02e66255 100644
--- a/test/output/build/config/index.html
+++ b/test/output/build/config/index.html
@@ -41,6 +41,9 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
+  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
+  if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
 <div id="observablehq-center">
 <main id="observablehq-main" class="observablehq">
diff --git a/test/output/build/config/one.html b/test/output/build/config/one.html
index 6404db548..650732177 100644
--- a/test/output/build/config/one.html
+++ b/test/output/build/config/one.html
@@ -41,6 +41,9 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
+  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
+  if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
 <div id="observablehq-center">
 <main id="observablehq-main" class="observablehq">
diff --git a/test/output/build/config/sub/two.html b/test/output/build/config/sub/two.html
index d06f97028..fd7b9b239 100644
--- a/test/output/build/config/sub/two.html
+++ b/test/output/build/config/sub/two.html
@@ -41,6 +41,9 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
+  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
+  if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
 <div id="observablehq-center">
 <main id="observablehq-main" class="observablehq">
diff --git a/test/output/build/config/toc-override.html b/test/output/build/config/toc-override.html
index acfb0b134..8efcf9909 100644
--- a/test/output/build/config/toc-override.html
+++ b/test/output/build/config/toc-override.html
@@ -41,6 +41,9 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
+  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
+  if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
 <aside id="observablehq-toc" data-selector="#observablehq-main h1:not(:first-of-type), #observablehq-main h2:not(h1 + h2)">
 <nav>
diff --git a/test/output/build/config/toc.html b/test/output/build/config/toc.html
index 0732e17ae..e70e346eb 100644
--- a/test/output/build/config/toc.html
+++ b/test/output/build/config/toc.html
@@ -41,6 +41,9 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
+  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
+  if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
 <aside id="observablehq-toc" data-selector="#observablehq-main h1:not(:first-of-type), #observablehq-main h2:not(h1 + h2)">
 <nav>
diff --git a/test/output/build/fetches/foo.html b/test/output/build/fetches/foo.html
index 0b4f18c51..3b979347f 100644
--- a/test/output/build/fetches/foo.html
+++ b/test/output/build/fetches/foo.html
@@ -43,6 +43,9 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
+  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
+  if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
 <div id="observablehq-center">
 <main id="observablehq-main" class="observablehq">
diff --git a/test/output/build/fetches/top.html b/test/output/build/fetches/top.html
index 63d76c9ba..e52f74cb3 100644
--- a/test/output/build/fetches/top.html
+++ b/test/output/build/fetches/top.html
@@ -46,6 +46,9 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
+  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
+  if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
 <div id="observablehq-center">
 <main id="observablehq-main" class="observablehq">
diff --git a/test/output/build/files/files.html b/test/output/build/files/files.html
index cb669674b..7c65f0733 100644
--- a/test/output/build/files/files.html
+++ b/test/output/build/files/files.html
@@ -57,6 +57,9 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
+  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
+  if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
 <div id="observablehq-center">
 <main id="observablehq-main" class="observablehq">
diff --git a/test/output/build/files/subsection/subfiles.html b/test/output/build/files/subsection/subfiles.html
index 6542676b3..0b3c1c2f9 100644
--- a/test/output/build/files/subsection/subfiles.html
+++ b/test/output/build/files/subsection/subfiles.html
@@ -57,6 +57,9 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
+  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
+  if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
 <div id="observablehq-center">
 <main id="observablehq-main" class="observablehq">
diff --git a/test/output/build/imports/foo/foo.html b/test/output/build/imports/foo/foo.html
index 62a416035..af5cb275b 100644
--- a/test/output/build/imports/foo/foo.html
+++ b/test/output/build/imports/foo/foo.html
@@ -49,6 +49,9 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
+  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
+  if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
 <div id="observablehq-center">
 <main id="observablehq-main" class="observablehq">
diff --git a/test/output/build/missing-file/index.html b/test/output/build/missing-file/index.html
index fc2dba3e8..8a254f556 100644
--- a/test/output/build/missing-file/index.html
+++ b/test/output/build/missing-file/index.html
@@ -39,6 +39,9 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
+  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
+  if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
 <div id="observablehq-center">
 <main id="observablehq-main" class="observablehq">
diff --git a/test/output/build/missing-import/index.html b/test/output/build/missing-import/index.html
index 2ac204997..5749beeed 100644
--- a/test/output/build/missing-import/index.html
+++ b/test/output/build/missing-import/index.html
@@ -40,6 +40,9 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
+  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
+  if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
 <div id="observablehq-center">
 <main id="observablehq-main" class="observablehq">
diff --git a/test/output/build/multi/index.html b/test/output/build/multi/index.html
index c974ed8fd..6d1423a34 100644
--- a/test/output/build/multi/index.html
+++ b/test/output/build/multi/index.html
@@ -50,6 +50,9 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
+  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
+  if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
 <div id="observablehq-center">
 <main id="observablehq-main" class="observablehq">
diff --git a/test/output/build/multi/subsection/index.html b/test/output/build/multi/subsection/index.html
index 0b09dfbbe..1e566f4e5 100644
--- a/test/output/build/multi/subsection/index.html
+++ b/test/output/build/multi/subsection/index.html
@@ -34,6 +34,9 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
+  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
+  if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
 <div id="observablehq-center">
 <main id="observablehq-main" class="observablehq">
diff --git a/test/output/build/simple-public/index.html b/test/output/build/simple-public/index.html
index e0addfbad..df09d8f68 100644
--- a/test/output/build/simple-public/index.html
+++ b/test/output/build/simple-public/index.html
@@ -33,6 +33,9 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
+  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
+  if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
 <div id="observablehq-center">
 <main id="observablehq-main" class="observablehq">
diff --git a/test/output/build/simple/simple.html b/test/output/build/simple/simple.html
index ef7c5235a..96a35b76e 100644
--- a/test/output/build/simple/simple.html
+++ b/test/output/build/simple/simple.html
@@ -42,6 +42,9 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
+  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
+  if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
 <div id="observablehq-center">
 <main id="observablehq-main" class="observablehq">
diff --git a/test/output/build/subtitle/index.html b/test/output/build/subtitle/index.html
index 9e3aee92a..5a8ad598a 100644
--- a/test/output/build/subtitle/index.html
+++ b/test/output/build/subtitle/index.html
@@ -33,6 +33,9 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
+  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
+  if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
 <aside id="observablehq-toc" data-selector="#observablehq-main h1:not(:first-of-type), #observablehq-main h2:not(h1 + h2)">
 <nav>

From 2b898534e8ae055f9c0790896d84fd160393ecbc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Philippe=20Rivi=C3=A8re?= <fil@rezo.net>
Date: Mon, 4 Dec 2023 16:40:26 +0100
Subject: [PATCH 3/4] apply recommendation from review

---
 src/render.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/render.ts b/src/render.ts
index 2727efb4b..e488b3cb3 100644
--- a/src/render.ts
+++ b/src/render.ts
@@ -138,7 +138,7 @@ function renderSidebar(title = "Home", pages: (Page | Section)[], path: string):
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
-  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  addEventListener("beforeunload", () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop));
   const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
   if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>`;

From 4a6a9bd37e6da9a33ec9e59fcacbb54a6f02f1e0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Philippe=20Rivi=C3=A8re?= <fil@rezo.net>
Date: Mon, 4 Dec 2023 16:40:48 +0100
Subject: [PATCH 4/4] fix tests

---
 test/output/build/archives/tar.html              | 2 +-
 test/output/build/archives/zip.html              | 2 +-
 test/output/build/config/closed/page.html        | 2 +-
 test/output/build/config/index.html              | 2 +-
 test/output/build/config/one.html                | 2 +-
 test/output/build/config/sub/two.html            | 2 +-
 test/output/build/config/toc-override.html       | 2 +-
 test/output/build/config/toc.html                | 2 +-
 test/output/build/fetches/foo.html               | 2 +-
 test/output/build/fetches/top.html               | 2 +-
 test/output/build/files/files.html               | 2 +-
 test/output/build/files/subsection/subfiles.html | 2 +-
 test/output/build/imports/foo/foo.html           | 2 +-
 test/output/build/missing-file/index.html        | 2 +-
 test/output/build/missing-import/index.html      | 2 +-
 test/output/build/multi/index.html               | 2 +-
 test/output/build/multi/subsection/index.html    | 2 +-
 test/output/build/simple-public/index.html       | 2 +-
 test/output/build/simple/simple.html             | 2 +-
 test/output/build/subtitle/index.html            | 2 +-
 20 files changed, 20 insertions(+), 20 deletions(-)

diff --git a/test/output/build/archives/tar.html b/test/output/build/archives/tar.html
index 9f6c8a885..1ffc9ffb0 100644
--- a/test/output/build/archives/tar.html
+++ b/test/output/build/archives/tar.html
@@ -76,7 +76,7 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
-  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  addEventListener("beforeunload", () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop));
   const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
   if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
diff --git a/test/output/build/archives/zip.html b/test/output/build/archives/zip.html
index 9a34b9c03..bb45db1c9 100644
--- a/test/output/build/archives/zip.html
+++ b/test/output/build/archives/zip.html
@@ -62,7 +62,7 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
-  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  addEventListener("beforeunload", () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop));
   const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
   if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
diff --git a/test/output/build/config/closed/page.html b/test/output/build/config/closed/page.html
index 82577a191..5cb8c2de8 100644
--- a/test/output/build/config/closed/page.html
+++ b/test/output/build/config/closed/page.html
@@ -41,7 +41,7 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
-  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  addEventListener("beforeunload", () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop));
   const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
   if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
diff --git a/test/output/build/config/index.html b/test/output/build/config/index.html
index a02e66255..8a2bd79b4 100644
--- a/test/output/build/config/index.html
+++ b/test/output/build/config/index.html
@@ -41,7 +41,7 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
-  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  addEventListener("beforeunload", () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop));
   const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
   if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
diff --git a/test/output/build/config/one.html b/test/output/build/config/one.html
index 650732177..d03e9a104 100644
--- a/test/output/build/config/one.html
+++ b/test/output/build/config/one.html
@@ -41,7 +41,7 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
-  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  addEventListener("beforeunload", () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop));
   const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
   if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
diff --git a/test/output/build/config/sub/two.html b/test/output/build/config/sub/two.html
index fd7b9b239..fd35cee41 100644
--- a/test/output/build/config/sub/two.html
+++ b/test/output/build/config/sub/two.html
@@ -41,7 +41,7 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
-  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  addEventListener("beforeunload", () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop));
   const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
   if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
diff --git a/test/output/build/config/toc-override.html b/test/output/build/config/toc-override.html
index 8efcf9909..72a0c0ec6 100644
--- a/test/output/build/config/toc-override.html
+++ b/test/output/build/config/toc-override.html
@@ -41,7 +41,7 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
-  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  addEventListener("beforeunload", () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop));
   const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
   if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
diff --git a/test/output/build/config/toc.html b/test/output/build/config/toc.html
index e70e346eb..13109d399 100644
--- a/test/output/build/config/toc.html
+++ b/test/output/build/config/toc.html
@@ -41,7 +41,7 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
-  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  addEventListener("beforeunload", () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop));
   const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
   if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
diff --git a/test/output/build/fetches/foo.html b/test/output/build/fetches/foo.html
index 3b979347f..2a25d703b 100644
--- a/test/output/build/fetches/foo.html
+++ b/test/output/build/fetches/foo.html
@@ -43,7 +43,7 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
-  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  addEventListener("beforeunload", () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop));
   const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
   if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
diff --git a/test/output/build/fetches/top.html b/test/output/build/fetches/top.html
index e52f74cb3..fb6bf4afe 100644
--- a/test/output/build/fetches/top.html
+++ b/test/output/build/fetches/top.html
@@ -46,7 +46,7 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
-  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  addEventListener("beforeunload", () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop));
   const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
   if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
diff --git a/test/output/build/files/files.html b/test/output/build/files/files.html
index 7c65f0733..3953a13e6 100644
--- a/test/output/build/files/files.html
+++ b/test/output/build/files/files.html
@@ -57,7 +57,7 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
-  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  addEventListener("beforeunload", () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop));
   const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
   if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
diff --git a/test/output/build/files/subsection/subfiles.html b/test/output/build/files/subsection/subfiles.html
index 0b3c1c2f9..2b1adf9c3 100644
--- a/test/output/build/files/subsection/subfiles.html
+++ b/test/output/build/files/subsection/subfiles.html
@@ -57,7 +57,7 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
-  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  addEventListener("beforeunload", () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop));
   const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
   if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
diff --git a/test/output/build/imports/foo/foo.html b/test/output/build/imports/foo/foo.html
index af5cb275b..ebca04684 100644
--- a/test/output/build/imports/foo/foo.html
+++ b/test/output/build/imports/foo/foo.html
@@ -49,7 +49,7 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
-  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  addEventListener("beforeunload", () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop));
   const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
   if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
diff --git a/test/output/build/missing-file/index.html b/test/output/build/missing-file/index.html
index 8a254f556..8d7355a32 100644
--- a/test/output/build/missing-file/index.html
+++ b/test/output/build/missing-file/index.html
@@ -39,7 +39,7 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
-  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  addEventListener("beforeunload", () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop));
   const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
   if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
diff --git a/test/output/build/missing-import/index.html b/test/output/build/missing-import/index.html
index 5749beeed..cee15c7d2 100644
--- a/test/output/build/missing-import/index.html
+++ b/test/output/build/missing-import/index.html
@@ -40,7 +40,7 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
-  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  addEventListener("beforeunload", () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop));
   const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
   if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
diff --git a/test/output/build/multi/index.html b/test/output/build/multi/index.html
index 6d1423a34..018cb2b73 100644
--- a/test/output/build/multi/index.html
+++ b/test/output/build/multi/index.html
@@ -50,7 +50,7 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
-  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  addEventListener("beforeunload", () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop));
   const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
   if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
diff --git a/test/output/build/multi/subsection/index.html b/test/output/build/multi/subsection/index.html
index 1e566f4e5..7184e47fc 100644
--- a/test/output/build/multi/subsection/index.html
+++ b/test/output/build/multi/subsection/index.html
@@ -34,7 +34,7 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
-  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  addEventListener("beforeunload", () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop));
   const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
   if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
diff --git a/test/output/build/simple-public/index.html b/test/output/build/simple-public/index.html
index df09d8f68..76415d765 100644
--- a/test/output/build/simple-public/index.html
+++ b/test/output/build/simple-public/index.html
@@ -33,7 +33,7 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
-  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  addEventListener("beforeunload", () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop));
   const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
   if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
diff --git a/test/output/build/simple/simple.html b/test/output/build/simple/simple.html
index 96a35b76e..31eb70bc3 100644
--- a/test/output/build/simple/simple.html
+++ b/test/output/build/simple/simple.html
@@ -42,7 +42,7 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
-  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  addEventListener("beforeunload", () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop));
   const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
   if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>
diff --git a/test/output/build/subtitle/index.html b/test/output/build/subtitle/index.html
index 5a8ad598a..3715e57d3 100644
--- a/test/output/build/subtitle/index.html
+++ b/test/output/build/subtitle/index.html
@@ -33,7 +33,7 @@
       case "false": if (!details.classList.contains("observablehq-section-active")) details.open = false; break;
     }
   }
-  window.onbeforeunload = () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop);
+  addEventListener("beforeunload", () => sessionStorage.setItem("observablehq-sidebar-scrolly", document.querySelector("#observablehq-sidebar").scrollTop));
   const scrolly = +sessionStorage.getItem("observablehq-sidebar-scrolly");
   if (scrolly) document.querySelector("#observablehq-sidebar").scrollTop = scrolly;
 }</script>