use iFrameId const

src/assets/init.js

@@ -1,3 +1,5 @@
+const iFrameId = 'main';
+
 var _ArrayBufferToBase64 = function (array_buffer) {
     var binary = '';
     var bytes = new Uint8Array(array_buffer);
@@ -21,13 +23,13 @@ var _base64ToArrayBuffer = function (base64) {
 };
 
 var createIframe = function() {
-    var iframe = document.getElementById('main');
+    var iframe = document.getElementById(iFrameId);
     if (iframe) { iframe.remove() };
     iframe = document.createElement("iframe");
     window.document.body.prepend(iframe);
     iframe.setAttribute('src', '#');
-    iframe.setAttribute('name', 'main');
+    iframe.setAttribute('name', iFrameId);
-    iframe.setAttribute('id', 'main');
+    iframe.setAttribute('id', iFrameId);
     iframe.style.display = 'none';
     return iframe;
 }
@@ -60,14 +62,14 @@ window.onload = function() {
             // iframe has finished loading and sent us its title
             // parent sets the title and responds with the data object
             window.document.title = evnt.data.argument;
-            var iframe = document.getElementById('main');
+            var iframe = document.getElementById(iFrameId);
             iframe.contentWindow.postMessage({
                 action: "set_data",
                 argument: window.data,
             }, "*");
         } else if (evnt.data.action == 'virtual_click') {
             // user has clicked on a link in the iframe
-            var iframe = document.getElementById('main');
+            var iframe = document.getElementById(iFrameId);
             iframe.remove()
             var loading = document.getElementById('loading-indicator');
             loading.style.display = '';
@@ -79,7 +81,7 @@ window.onload = function() {
         } else if (evnt.data.action == 'show_iframe') {
             // iframe finished fixing the document and is ready to be shown;
             // hide loading indicator
-            var iframe = document.getElementById('main');
+            var iframe = document.getElementById(iFrameId);
             iframe.style.display = '';
             var loading = document.getElementById('loading-indicator');
             loading.style.display = 'none';

src/assets/inject.js

@@ -197,6 +197,7 @@ window.addEventListener("message", (evnt) => {
                 cancelable: true
             }));
         } finally {
+            observer.observe(window.document.body, {subtree: true, childList: true});
             window.parent.postMessage({
                 action: "show_iframe",
                 argument: "",
@@ -222,7 +223,6 @@ const observer = new MutationObserver((mutationList) => {
         }
     });
 });
-observer.observe(window.document.body, {subtree: true, childList: true});
 
 
 // Set parent window title and trigger data transmission

src/embed.py

@@ -149,19 +149,20 @@ def embed_html_resources(html, base_dir, before, after):
 
     import bs4
     soup = bs4.BeautifulSoup(html, 'lxml')
+    body = soup.find('body')
 
-    if before:
+    if body and before:
         script = soup.new_tag("script")
         script.string = before
-        soup.find('body').insert(0, script)
+        body.insert(0, script)
 
-    if after:
+    if body and after:
         script = soup.new_tag("script")
         script.string = after
-        soup.find('body').append(script)
+        body.append(script)
 
     # TODO embed remote resources in case we want the entire file to be
-    # usable in an offline environment 
+    # usable in an offline environment
 
     return str(soup)