feat: Add JavaScript core exercises and solutions

- Implemented exercises for array high-order methods, memory and execution, switch statements, and final review.
- Added starter and answer files for each exercise to facilitate learning.
- Created a runner HTML file to execute JavaScript code and display console outputs.
- Updated README files to include exercise objectives, tasks, and usage instructions.

03-javascript-core/16-final-review/answer.js

@@ -0,0 +1,70 @@
+const reviewer = {
+  name: "林晨",
+  stage: "final-review",
+  showTitle() {
+    console.log(`${this.name} 的学习营总复盘`);
+  },
+};
+
+const lessons = [
+  { title: "变量", score: 80, finished: true },
+  { title: "闭包", score: 92, finished: true },
+  { title: "this", score: 87, finished: true },
+  { title: "补漏练习", score: null, finished: false },
+  { title: "综合回顾", score: 95, finished: true },
+];
+
+let mentorNote;
+const reviewComment = null;
+
+function getStageText(stage) {
+  switch (stage) {
+    case "basic":
+      return "基础阶段";
+    case "advanced":
+      return "补充阶段";
+    case "final-review":
+      return "总复习阶段";
+    default:
+      return "未知阶段";
+  }
+}
+
+reviewer.showTitle();
+console.log("阶段说明：", getStageText(reviewer.stage));
+console.log("mentorNote 是否为 undefined：", mentorNote === undefined);
+console.log("reviewComment 是否为 null：", reviewComment === null);
+
+const validLessons = [];
+
+for (let index = 0; index < lessons.length; index += 1) {
+  const lesson = lessons[index];
+
+  if (lesson.score === undefined || lesson.score === null) {
+    console.log(`在《${lesson.title}》处遇到空成绩，停止读取后续项目。`);
+    break;
+  }
+
+  validLessons.push(lesson);
+}
+
+const lessonTitles = validLessons.map(function (lesson) {
+  return lesson.title;
+});
+
+const averageScore =
+  validLessons.reduce(function (total, lesson) {
+    return total + lesson.score;
+  }, 0) / validLessons.length;
+
+const allFinished = validLessons.every(function (lesson) {
+  return lesson.finished === true;
+});
+
+const reviewerAlias = reviewer;
+reviewerAlias.stage = "advanced";
+
+console.log("引用修改后的 reviewer.stage：", reviewer.stage);
+console.log("有效课程：", lessonTitles.join("、"));
+console.log("平均分：", averageScore);
+console.log("是否全部完成：", allFinished);