Fix duplicate practice answers

Fixe #3

flashcard.js

@@ -1,19 +1,18 @@
-const randomItem = (not) => {
-  let item;
-
-  do {
-    const idx = Math.floor(Math.random() * window.ITEMS.length);
-    item = window.ITEMS[idx];
-  } while (not && item === not);
-
-  return item;
-};
-
 const infoText = document.querySelector("#info-text");
 
 function next() {
   infoText.textContent = "";
-  const item = randomItem();
+
+  const candiates = [...window.ITEMS];
+
+  const nextRandomItem = () => {
+    const idx = Math.floor(Math.random() * candiates.length);
+    const result = candiates[idx];
+    candiates.splice(idx, 1);
+    return result;
+  };
+
+  const item = nextRandomItem();
 
   const mangle = Math.random() > 0.5;
 
@@ -24,10 +23,10 @@ function next() {
   children[1].textContent = mangle ? item.means : item.mangle;
 
   const options = [
-    randomItem(item),
-    randomItem(item),
-    randomItem(item),
-    randomItem(item),
+    nextRandomItem(item),
+    nextRandomItem(item),
+    nextRandomItem(item),
+    nextRandomItem(item),
   ];
   const correctIdx = Math.floor(Math.random() * options.length);
   options[correctIdx] = item;