Add back button

src/fsm.js

@@ -9,6 +9,7 @@ const buttons = /** @type {HTMLDivElement} */ (document.getElementById('input-bu
 const controlsButton = /** @type {HTMLButtonElement} */ (document.getElementById('controls-button'));
 const clearButton = /** @type {HTMLButtonElement} */ (document.getElementById('clear-button'));
 const light = /** @type {HTMLDivElement} */ (document.getElementById('light'));
+const container = /** @type {HTMLDivElement} */ (document.getElementById('state-graph'));
 
 /**
  * @param {import('./examples.js').State[]} states
@@ -34,7 +35,9 @@ export function openAutomaton(states, editable = false) {
       console.error(e);
     }
   });
-  const container = /** @type {HTMLDivElement} */ (document.getElementById('state-graph'));
+  while (container.firstChild) {
+    container.removeChild(container.firstChild);
+  }
   container.appendChild(viewer);
   viewer.graph = graph;
 
@@ -83,21 +86,30 @@ export function openAutomaton(states, editable = false) {
     updateUIState();
   }
 
-  // Dynamically create buttons for each letter in the alphabet
   /**
-   * @type {string[]}
+   * Dynamically create buttons for each letter in the alphabet.
    */
-  const alphabet = Array.from(states.reduce((acc, current) => {
-    Object.keys(current.transitions).forEach(current => acc.add(current));
-    return acc;
-  }, new Set())).sort();
-  for (const letter of alphabet) {
-    const button = document.createElement('button');
-    button.innerText = letter;
-    button.addEventListener('click', () => step(letter));
-    buttons.appendChild(button);
+  function createLetters() {
+    /**
+     * @type {string[]}
+     */
+    const alphabet = Array.from(states.reduce((acc, current) => {
+      Object.keys(current.transitions).forEach(current => acc.add(current));
+      return acc;
+    }, new Set())).sort();
+    while (buttons.firstChild) {
+      buttons.removeChild(buttons.firstChild);
+    }
+    for (const letter of alphabet) {
+      const button = document.createElement('button');
+      button.innerText = letter;
+      button.addEventListener('click', () => step(letter));
+      buttons.appendChild(button);
+    }
   }
 
+  createLetters();
+
   // Reacts to input in the text box
   wordInput.addEventListener('input', () => type());