function startExercise() {
const grade = document.getElementById("grade").value;
const book = document.getElementById("book").value;
const mode = document.getElementById("mode").value;
currentWords = [...wordData[grade][book]]; //
复制单词数据
document.getElementById("exercise-area").innerHTML = ""
;
document.getElementById("word-list").style.display =
"none";
document.getElementById("report").style.display =
"none";
function showNextWord(mode) {
if (currentWords.length === 0 && errors.length === 0) {
word = errors.shift(); // 优先处理错误单词