diff --git a/edit/codemirror-factory.js b/edit/codemirror-factory.js
index d2b201b3..b1d89f08 100644
--- a/edit/codemirror-factory.js
+++ b/edit/codemirror-factory.js
@@ -138,10 +138,11 @@ const cmFactory = (() => {
   }
 
   function autocompleteOnTyping(cm, [info], debounced) {
+    const lastLine = info.text[info.text.length - 1];
     if (
       cm.state.completionActive ||
       info.origin && !info.origin.includes('input') ||
-      !info.text.last
+      !lastLine
     ) {
       return;
     }
@@ -153,7 +154,7 @@ const cmFactory = (() => {
       debounce(autocompleteOnTyping, 100, cm, [info], true);
       return;
     }
-    if (info.text.last.match(/[-a-z!]+$/i)) {
+    if (lastLine.match(/[-a-z!]+$/i)) {
       cm.state.autocompletePicked = false;
       cm.options.hintOptions.completeSingle = false;
       cm.execCommand('autocomplete');
diff --git a/edit/sections-editor.js b/edit/sections-editor.js
index 2fb69ada..27607d66 100644
--- a/edit/sections-editor.js
+++ b/edit/sections-editor.js
@@ -476,6 +476,7 @@ function createSectionsEditor(style) {
 
   function removeSection(section) {
     if (sections.every(s => s.isRemoved() || s === section)) {
+      // TODO: hide remove button when `#sections[data-section-count=1]`
       throw new Error('Cannot remove last section');
     }
     if (section.cm.isBlank()) {
@@ -534,7 +535,6 @@ function createSectionsEditor(style) {
       container.appendChild(section.el);
     }
     section.render();
-    // maximizeCodeHeight(section.el);
     updateSectionOrder();
     section.onChange(updateLivePreview);
     updateLivePreview();
diff --git a/js/dom.js b/js/dom.js
index a1ae0180..86445043 100644
--- a/js/dom.js
+++ b/js/dom.js
@@ -13,23 +13,6 @@ if (!/^Win\d+/.test(navigator.platform)) {
   NodeList.prototype[method] = Array.prototype[method];
 });
 
-// eslint-disable-next-line no-extend-native
-Object.defineProperties(Array.prototype, {
-  last: {
-    get() {
-      return this[this.length - 1];
-    },
-  },
-  rotate: {
-    value: function (amount) {
-      // negative amount == rotate left
-      const r = this.slice(-amount, this.length);
-      Array.prototype.push.apply(r, this.slice(0, this.length - r.length));
-      return r;
-    },
-  },
-});
-
 // polyfill for old browsers to enable [...results] and for-of
 for (const type of [NodeList, NamedNodeMap, HTMLCollection, HTMLAllCollection]) {
   if (!type.prototype[Symbol.iterator]) {