Update main.js

expanding-list-web-component/main.js

@@ -1,60 +1,58 @@
 // Create a class for the element
 class ExpandingList extends HTMLUListElement {
-  constructor() {
-    // Always call super first in constructor
-    // Return value from super() is a reference to this element
-    self = super();
-  }
-
   connectedCallback() {
     // Get ul and li elements that are a child of this custom ul element
     // li elements can be containers if they have uls within them
-    const uls = Array.from(self.querySelectorAll("ul"));
-    const lis = Array.from(self.querySelectorAll("li"));
+    const uls = this.querySelectorAll('ul');
+    const lis = this.querySelectorAll('li');
+
     // Hide all child uls
     // These lists will be shown when the user clicks a higher level container
-    uls.forEach((ul) => {
-      ul.style.display = "none";
-    });
+    for (const ul of uls) {
+      ul.style.display = 'none';
+    }
 
     // Look through each li element in the ul
-    lis.forEach((li) => {
+    for (const li of lis) {
       // If this li has a ul as a child, decorate it and add a click handler
-      if (li.querySelectorAll("ul").length > 0) {
-        // Add an attribute which can be used  by the style
+      if (li.querySelectorAll('ul').length > 0) {
+        // Add an attribute which can be used by the style
         // to show an open or closed icon
-        li.setAttribute("class", "closed");
+        li.setAttribute('class', 'closed');
 
         // Wrap the li element's text in a new span element
         // so we can assign style and event handlers to the span
         const childText = li.childNodes[0];
-        const newSpan = document.createElement("span");
+        const newSpan = document.createElement('span');
 
         // Copy text from li to span, set cursor style
         newSpan.textContent = childText.textContent;
-        newSpan.style.cursor = "pointer";
+        newSpan.style.cursor = 'pointer';
 
         // Add click handler to this span
-        newSpan.addEventListener("click", (e) => {
+        const onClick = (e) => {
           // next sibling to the span should be the ul
-          const nextul = e.target.nextElementSibling;
+          const nextUl = e.target.nextElementSibling;
 
           // Toggle visible state and update class attribute on ul
-          if (nextul.style.display == "block") {
-            nextul.style.display = "none";
-            nextul.parentNode.setAttribute("class", "closed");
+          if (nextUl.style.display === 'block') {
+            nextUl.style.display = 'none';
+            nextUl.parentNode.setAttribute('class', 'closed');
           } else {
-            nextul.style.display = "block";
-            nextul.parentNode.setAttribute("class", "open");
+            nextUl.style.display = 'block';
+            nextUl.parentNode.setAttribute('class', 'open');
           }
-        });
+        };
+
+        newSpan.addEventListener('click', onClick);
+
         // Add the span and remove the bare text node from the li
-        childText.parentNode.insertBefore(newSpan, childText);
-        childText.parentNode.removeChild(childText);
+        childText.parentNode?.insertBefore(newSpan, childText);
+        childText.parentNode?.removeChild(childText);
       }
-    });
+    }
   }
 }
 
 // Define the new element
-customElements.define("expanding-list", ExpandingList, { extends: "ul" });
+customElements.define('expanding-list', ExpandingList, { extends: 'ul' });