我已经创建了一个程序，该程序应该为每页10个学生分页。共有54名学生。
我已将所有学生列表项添加到一个对象数组中。
然后我隐藏了学生的所有原始html，并根据点击的分页链接，然后它将显示从对象数组中获取的正确数量的学生。
由于某些原因，在我的displayPagination()函数中，显示的错误是我的包装器没有被添加到页面中，因此程序都不起作用。它说＆＃34; app.js：167 Uncaught TypeError：无法读取属性＆quot; appendChild＆＃39;未定义＆＃34;。
知道这里发生了什么吗？
请忽略我对底部搜索功能的评论。我还没有实现。
//Problem: Shows too many people per page
//Solution: Incorporate pagination and add search functionality
'useStrict';
//Find total number of students
var studentTotal = document.getElementsByClassName("student-item").length;
var itemsToShowPerPage = 10;
//empty array of objects for students
var studentArray = [];
//Call buildSearch()
buildSearch();
//display initial page
initialDisplay();
//Cach DOM elements for easy access
var page = document.querySelector(".page");
var paginationLink = document.getElementsByClassName("pagination-link");
var studentList = document.querySelector(".student-list");
function studentShow(start, end) {
studentList.innerHTML = '';
for(var i = start; i <= end; i++){
var newStudent = displayStudents(studentArray[i]);
studentList.appendChild(newStudent);
}
}
//Calculate the number of pages needed
function calculatePageCount() {
var pagesNeeded = Math.ceil(studentTotal/itemsToShowPerPage);
console.log("Amount of pages needed :" + pagesNeeded);
return pagesNeeded;
}
//builds search
function buildSearch () {
var pageHeader = document.querySelector('.page-header');
var searchWrap = document.createElement('div');
var searchInput = document.createElement('input');
var searchButton = document.createElement('button');
searchWrap.classList.add('student-search');
searchButton.classList.add('search-button');
searchInput.setAttribute('placeholder', 'Search for students...');
searchInput.classList.add('student-search-input');
searchButton.textContent = ('Search');
searchWrap.appendChild(searchInput);
searchWrap.appendChild(searchButton);
pageHeader.appendChild(searchWrap);
}
//create student object
function studentObject(name, avatar, email, dateJoined) {
this.name = name;
this.avatar = avatar;
this.email = email;
this.dateJoined = dateJoined;
}
//filter students and create an array of objects
function studentFilter() {
var student, name, avatar, email, dateJoined;
var studentList = document.querySelectorAll('.student-list')[0].children;
for(var i = 0; i < studentList.length; i++) {
avatar = studentList[i].children[0].children[0].src;
name = studentList[i].children[0].children[1].innerHTML;
email = studentList[i].children[0].children[2].innerHTML;
dateJoined = studentList[i].children[1].children[0].innerHTML;
//create new object
student = new studentObject(name,avatar, email, dateJoined);
//add each student into the array for later use
studentArray.push(student);
}
}
//construct html for student
function displayStudents(student) {
var listItem, detailsDiv, joinedDetails, avatarImg, nameH, emailSpan, date;
//Create student list item
listItem = document.createElement('li');
//add it's classes
listItem.classList.add('student-item');
listItem.classList.add('cf');
//create first div for student details
detailsDiv = document.createElement('div');
//add it's class
detailsDiv.classList.add('student-details');
//create the details to go into detailsDiv
avatarImg = document.createElement('img');
avatarImg.src = student.avatar;
nameH = document.createElement('h3');
nameH.innerHTML = student.name;
emailSpan = document.createElement('span');
email.innerHTML = student.email;
//add their classes
avatarImg.classList.add('avatar');
emailSpan.classList.add('email');
//add details to detailsDiv
detailsDiv.appendChild(avatarImg);
detailsDiv.appendChild(emailSpan);
detailsDiv.appendChild(nameH);
//create second div for joinedDetails
joinedDetails = document.createElement('div');
//add it's class
joinedDetails.classList.add('joined-details');
//create date to put into joinedDetails
date = document.createElement('span');
date.innerHTML = student.dateJoined;
//add it's class
date.classList.add('date');
//add date to joinDetails
joinedDetails.appendChild(date);
//add divs to listItem
listItem.appendChild(detailsDiv);
listItem.appendChild(joinedDetails);
return listItem;
}
function displayPaginationLinks() {
var link, pagLink;
//create template
var wrapper = document.createElement('div');
wrapper.classList.add('pagination');
var pagList = document.createElement('ul');
pagList.classList.add("pagination-links");
wrapper.appendChild(pagList);
var pageCount = calculatePageCount();
//add individual elements
for(var i = 1; i <= pageCount; i++) {
pagLink = document.createElement('li');
link = document.createElement('a');
link.innerHTML = i;
link.href = "#";
pagLink.appendChild(link);
pagList.appendChild(pagLink);
}
//make first link 'active'
pagList.children[0].children[0].classList.add("active");
//add to wrapper
wrapper.appendChild(pagList);
//add wrapper to page
page.appendChild(wrapper);
}
function paginate(event) {
event.preventDefault();
//variables for
var start, end;
//reset link class
for(var i = 0; i < paginationLink.length; i++) {
paginationLink[i].className = "pagination-link";
}
//THIS link's class will be active
this.classList.add('active');
//show the right section of item lists
start = (this.innerHTML * 10) - 10;
end = (this.innerHTML * 10) - 1;
//make sure if end of list, only show the remaining few
if(end < studentArray.length){
end = studentArray.length -1;
}
studentShow(start, end);
}
function initialDisplay() {
studentFilter();
//displayStudents(studentArray);
if (calculatePageCount() > 1) {
displayPaginationLinks();
}
//show first 10 students
studentShow(0, 9);
}
//Add search function
//Using progressive enhancement, add the student search markup as presented in the filters-example.html file to the index.html file.
//Make sure it's case insensitive
//User can search by name or e-mail address. Also partial matches
//Dynamically filter the student listings.
//Results should also be paginated. Don't use jQuery
//If no matches are found, add HTML message to say so
//Event Listeners
//Search button
//Pagination
for(var i = 0; i < paginationLink.length; i++) {
paginationLink[i].addEventListener("click", paginate);
}
这是html：
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8"/>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<title>Students</title>
<link rel="stylesheet" href="css/reset.css">
<link rel="stylesheet" href="css/design.css">
</head>
<body>
<div class="page">
<div class="page-header cf">
<h2>Students</h2>
</div>
<ul class="student-list">
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/women/67.jpg">
<h3>iboya vat</h3>
<span class="email">iboya.vat@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 07/15/15</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/75.jpg">
<h3>aapo niskanen</h3>
<span class="email">aapo.niskanen@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 06/15/12</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/34.jpg">
<h3>phillip cox</h3>
<span class="email">phillip.cox@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 09/11/14</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/women/38.jpg">
<h3>zilda moreira</h3>
<span class="email">zilda.moreira@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 07/15/15</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/women/23.jpg">
<h3>lilou le gall</h3>
<span class="email">lilou.le gall@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 06/16/13</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/women/94.jpg">
<h3>lucy hall</h3>
<span class="email">lucy.hall@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 09/11/16</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/women/24.jpg">
<h3>mark colin</h3>
<span class="email">mark.colin@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 01/14/14</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/women/14.jpg">
<h3>sara alves</h3>
<span class="email">sara.alves@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 07/19/16</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/49.jpg">
<h3>ramon macrae</h3>
<span class="email">ramon.macrae@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 05/13/12</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/15.jpg">
<h3>connor taylor</h3>
<span class="email">connor.taylor@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 05/18/14</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/11.jpg">
<h3>aymeric morel</h3>
<span class="email">aymeric.morel@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 06/13/13</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/49.jpg">
<h3>lorenz otto</h3>
<span class="email">lorenz.otto@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 05/11/14</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/29.jpg">
<h3>karl williamson</h3>
<span class="email">karl.williamson@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 01/12/14</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/34.jpg">
<h3>ouassim heering</h3>
<span class="email">ouassim.heering@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 01/18/12</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/91.jpg">
<h3>roberto molina</h3>
<span class="email">roberto.molina@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 06/13/15</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/28.jpg">
<h3>jordan hubert</h3>
<span class="email">jordan.hubert@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 06/13/15</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/29.jpg">
<h3>melvin baker</h3>
<span class="email">melvin.baker@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 09/18/14</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/26.jpg">
<h3>everett gordon</h3>
<span class="email">everett.gordon@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 06/17/15</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/82.jpg">
<h3>aiden ma</h3>
<span class="email">aiden.ma@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 07/18/12</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/62.jpg">
<h3>florent gerard</h3>
<span class="email">florent.gerard@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 02/12/13</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/women/96.jpg">
<h3>amber chen</h3>
<span class="email">amber.chen@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 07/12/12</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/women/9.jpg">
<h3>alexandra davies</h3>
<span class="email">alexandra.davies@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 05/11/13</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/57.jpg">
<h3>sergio cole</h3>
<span class="email">sergio.cole@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 02/17/15</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/98.jpg">
<h3>edgar dixon</h3>
<span class="email">edgar.dixon@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 06/17/11</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/94.jpg">
<h3>kirk myers</h3>
<span class="email">kirk.myers@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 09/17/15</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/women/28.jpg">
<h3>ani hesseling</h3>
<span class="email">ani.hesseling@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 08/14/16</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/women/24.jpg">
<h3>victoire bonnet</h3>
<span class="email">victoire.bonnet@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 05/13/16</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/44.jpg">
<h3>marcos morales</h3>
<span class="email">marcos.morales@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 01/12/12</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/75.jpg">
<h3>nils neumann</h3>
<span class="email">nils.neumann@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 03/11/12</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/women/86.jpg">
<h3>emily harrison</h3>
<span class="email">emily.harrison@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 07/18/15</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/41.jpg">
<h3>matthew fortin</h3>
<span class="email">matthew.fortin@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 03/18/15</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/women/32.jpg">
<h3>charlotte steward</h3>
<span class="email">charlotte.steward@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 02/18/11</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/3.jpg">
<h3>marceau rodriguez</h3>
<span class="email">marceau.rodriguez@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 07/13/14</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/91.jpg">
<h3>hudson anderson</h3>
<span class="email">hudson.anderson@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 09/12/15</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/33.jpg">
<h3>warren phillips</h3>
<span class="email">warren.phillips@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 01/11/12</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/41.jpg">
<h3>leo niva</h3>
<span class="email">leo.niva@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 09/14/15</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/3.jpg">
<h3>hani prevoo</h3>
<span class="email">hani.prevoo@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 01/11/15</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/women/79.jpg">
<h3>veronica rodriguez</h3>
<span class="email">veronica.rodriguez@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 07/17/12</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/41.jpg">
<h3>ginestal das neves</h3>
<span class="email">ginestal.das neves@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 06/19/12</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/63.jpg">
<h3>devon barnes</h3>
<span class="email">devon.barnes@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 09/19/14</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/women/10.jpg">
<h3>elsa lahti</h3>
<span class="email">elsa.lahti@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 04/15/12</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/women/12.jpg">
<h3>soline leclercq</h3>
<span class="email">soline.leclercq@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 05/12/14</span>
</div>
</li>
<li class="student-item cf">
<div class="student-details">
<img class="avatar" src="https://randomuser.me/api/portraits/thumb/men/89.jpg">
<h3>henri kruse</h3>
<span class="email">henri.kruse@example.com</span>
</div>
<div class="joined-details">
<span class="date">Joined 05/14/13</span>
</div>
</li>
</ul>
</div>
</body>
<script type="text/javascript" src="js/app.js"></script>
</html>
答案 0 :(得分：1)
在向initialDisplay变量分配任何内容之前，问题似乎是调用page - 因此，page调用displayPaginationLinks时page.appendChild未定义。