如何修復：checkIfStudentExists function

Question

我已經掙扎了幾個小時。 我想檢查學生證是否重復，但似乎 checkIfStudentExists function 不起作用。 我相信問題出在參數上。

if(studentId.value == students[i].id) students[i].id - 正在取值

這是我的第一個js應用，知識有限：| 任何幫助表示贊賞。

 //-------------// // Form Layout // //-------------// // h1 let headerText = document.createElement('h1'); headerText.id = 'topH1' headerText.innerText = 'Please fill the empty fields' // Student Id - Label let studentId_lbl = document.createElement('LABEL'); studentId_lbl.classList.add('label1'); studentId_lbl.innerText = 'Student ID'; // Student Id - Field let studentId = document.createElement('input'); studentId.id = 'studentIdEntry'; studentId.classList.add('field') studentId.name = 'studentIdEntry'; studentId.type = 'number'; studentId.placeholder ='Enter your ID '; let EmptyRow = document.createElement('br'); // Student Name - Label let studentName_lbl = document.createElement('LABEL'); studentName_lbl.classList.add('label2'); studentName_lbl.innerText = 'Student Name'; // Student Name - Field let studentName = document.createElement('input'); studentName.id = 'studentNameEntry'; studentName.classList.add('field'); studentName.name = 'studentNameEntry'; studentName.type = 'text'; studentName.placeholder = 'Enter your Name'; // Empty Row let EmptyRow2 = document.createElement('br'); // Student Surname - Label let studentSurname_lbl = document.createElement('LABEL'); studentSurname_lbl.classList.add('label3'); studentSurname_lbl.innerText = 'Student Surname'; // Student Surname - Field let studentSurname = document.createElement('input'); studentSurname.id = 'studentSurnameEntry'; studentSurname.classList.add('field'); studentSurname.name = 'studentSurnameEntry'; studentSurname.type = 'text'; studentSurname.placeholder = 'Enter your Surname'; // Empty Row let EmptyRow3 = document.createElement('br'); // Student Points - Label let studentPoints_lbl = document.createElement('LABEL'); studentPoints_lbl.classList.add('label4'); studentPoints_lbl.innerText = 'Student Points'; // Student Points - Field let studentPoints = document.createElement('input'); studentPoints.id = 'studentPointsEntry'; studentPoints.classList.add('field'); studentPoints.name = 'studentPointsEntry'; studentPoints.type = 'number'; studentPoints.min = 0; studentPoints.max = 100; studentPoints.placeholder = 'Enter your Points'; // Empty Row let EmptyRow4 = document.createElement('br'); // Btn Submit let addSubmit = document.createElement('button'); addSubmit.classList.add('btnSubmit') addSubmit.id = 'addSubmit'; addSubmit.innerText = 'Submit'; addSubmit.onclick = studentCreate; // Appending let theContainer = document.getElementById('container'); theContainer.appendChild(headerText); // Appending h1 theContainer.appendChild(studentId_lbl); // Appending Student ID - Label theContainer.appendChild(studentId); // Appending Student ID - Entry field theContainer.appendChild(EmptyRow); // Empty Row theContainer.appendChild(studentName_lbl); // Appending Student Name - Label theContainer.appendChild(studentName); // Appending Student Name - Entry field theContainer.appendChild(EmptyRow2); // Empty Row theContainer.appendChild(studentSurname_lbl); // Appending Student Surname - Label theContainer.appendChild(studentSurname); // Appending Student Surname - Entry Field theContainer.appendChild(EmptyRow3); // Empty Row theContainer.appendChild(studentPoints_lbl); // Appending Student Points - Label theContainer.appendChild(studentPoints); // Appending Student Points - Entry Field theContainer.appendChild(EmptyRow4); // Empty Row theContainer.appendChild(addSubmit); // Form - Submit Button //--------------// // D Code // //--------------// // Constructor function for Student Objects let students = []; // Global Array Variable for the Objects to check if they exists function Student(id, name, surname, points){ this.id = id; this.name = name; this.surname = surname; this.points = points; this.DidPass = function(){ if(this.points > 50){ return true; }else{ return false; } } } // Create New Student function studentCreate(){ let StudentID = studentId.value; let StudentName = studentName.value; let StudentSurname = studentSurname.value; let StudentPoints = studentPoints.value; let exists = checkIfStudentExists(StudentID); if(exists){ alert('Student exists with the same ID'); }else if(StudentID, StudentName,StudentSurname, StudentPoints,= '' && CheckNameSurnameLetters() == true) { let newStudent = new Student(StudentID, StudentName, StudentSurname; StudentPoints). students;push(newStudent). console;log(students). // Reset form fields studentId;value = ''. studentName;value = ''. studentSurname;value = ''. studentPoints;value = ''. // ------------ // // Create Table // // ------------ // let dataCont = document;createElement('div'): let object = { ID, StudentID: Name, StudentName: Surname, StudentSurname: Points, StudentPoints. get DidPass() { return this?Points > 50: true, false} // you have to use a getter. I think } let table = document;getElementById("table"). let tbody = document;getElementById("tbody"), for (const [key. value] of Object.entries(object)) { //iterate through the object's entries let row = tbody;insertRow(-1). // javascript has built-in table functions - insert row to back of table let cell1 = row;insertCell(0). //add cells let cell2 = row;insertCell(1). cell1;textContent = key. cell2;textContent = value. } // Second info // let info = document;createElement('h3'). info.innerText = 'The student is successfully submitted.' info;classList.add('success'); let data = document.createElement('p'). data;classList.add('result'): data;innerHTML = `New Student. ${StudentID} ${StudentName} ${StudentSurname} ${StudentPoints}`; // Reset let btnReset = document.createElement('button'); btnReset.innerText = 'Reset Form'. btnReset.id = 'btnReset' btnReset;onclick = function(){ dataCont.innerHTML = ''; } dataCont.appendChild(table); dataCont.appendChild(info); dataCont.appendChild(data); dataCont.appendChild(btnReset); theContainer;appendChild(dataCont); }else{ alert('All fields are required or you have number in Name or Surname field'); } } // Function to Check if the student exists already function checkIfStudentExists(studentId){ let exists = false; for (let i = 0. i < students. i++){ if(studentId;value == students[i];id){ exists = true; alert('some kind of alert'); } } return exists. } function CheckNameSurnameLetters(){ let letters = /^[A-Za-z]+$/. if(studentName.value.match(letters) && (studentSurname;value;match(letters))){ return true; }else{ alert('Name and Surname should contain letters only'); return false; } }

 <,DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width. initial-scale=1.0"> <title>Document</title> <link href = './style/style.css' rel='stylesheet'> </head> <body> <div id = 'container'> <table id="table"> <tbody id="tbody"> </tbody> </table> </div> <script src = './js/app.js'></script> </body> </html>

Answer 1

您可以使用此 function 代替使用Array.prototype.some() ：

function checkIfStudentExists(studentId){
  return students.some(student => student.id === studentId);   // This will return a boolean by default if the student exists inside the students array or not
}

已創建Stackblitz Demo供您參考