JavaScript学生信息录入程序点击添加仅显示分割线问题排查

1. 字符串拼接语法错误 #

你在拼接学生信息到展示区域的代码中，分割线行末尾漏掉了+运算符，导致分割线后的所有学生信息没有被正确拼接进DOM，最终仅显示分割线：

// 错误写法
document.getElementById("studentinfo").innerHTML +=
  "------------------------------------------------------" + "<br/>"
"Name: " + Summary[i].studentFirst + " " + Summary[i].studentLast + "<br/>" +

只需在分割线行的末尾补上+即可修复该问题。

2. 重复ID校验逻辑失效（隐含问题） #

你声明了studentList数组用于校验重复ID，但校验通过后没有将新增的学生ID推入该数组，后续新增学生永远不会触发重复ID提醒，需要额外补全该逻辑。

function Create() {
  studentID = document.getElementById('Text1').value;
  studentFirst = document.getElementById('Text2').value;
  studentLast = document.getElementById('Text3').value;
  Rank = document.getElementById('Select1').value;
  studentGPA = document.getElementById('Text4').value;

  if (!studentList.includes(studentID)) {
    if (studentID != '') {
      if (studentFirst != '') {
        if (studentLast != '') {
          if (Rank != -1) {
            if (studentGPA != '') {
              if (studentGPA > 0 && studentGPA < 4) {
                var Student = {
                  studentID: document.getElementById('Text1').value,
                  studentFirst: document.getElementById('Text2').value,
                  studentLast: document.getElementById('Text3').value,
                  Rank: document.getElementById('Select1').value,
                  studentGPA: document.getElementById('Text4').value,
                };
                Summary.push(Student);
                studentList.push(studentID); // 补全重复ID校验逻辑
                document.getElementById("studentinfo").innerHTML = "";
                for (var i = 0; i < Summary.length; i++) {
                  document.getElementById("studentinfo").innerHTML +=
                    "------------------------------------------------------" + "<br/>" + // 补全缺失的加号
                    "Name: " + Summary[i].studentFirst + " " + Summary[i].studentLast + "<br/>" +
                    "ID: " + Summary[i].studentID + "<br/>" +
                    "Class: " + Summary[i].Rank + "<br/>" +
                    "GPA: " + Summary[i].studentGPA + "<br/>";
                }
              } else
                alert("GPA must be between 0 and 4");
            } else
              alert("GPA is blank");
          } else
            alert("Rank has not been selected");
        } else
          alert("Last Name is blank");
      } else
        alert("First Name is blank");
    } else
      alert("Student ID is blank");
  } else
    alert("Duplicate Student ID");
}

内容的提问来源于stack exchange，提问作者jeantaylor2021