you have the wrong class name
const controls = document.querySelector(".controls");
const container = document.querySelector(".thumbnailcontainer");
const allBox = container.children;
const containerWidth = container.offsetWidth;
const margin = 30;
var item = 0;
var totalItems = 0;
// item setup per slide
responsive =
[ { breakPoint: { width: 0, item: 1 }} // if width greater than 0 (1 will item show)
, { breakPoint: { width: 600, item: 2 }} // if width greater than 600 (2 will item show)
, { breakPoint: { width: 1000, item: 6 }} // if width greater than 1000 (4 will item show)
]
function load() {
for (let i = 0; i < responsive.length; i++) {
if (window.innerWidth > responsive[i].breakPoint.width) {
items = responsive[i].breakPoint.item
}
}
start();
}
function start() {
var totalItemsWidth = 0
for (let i = 0; i < allBox.length; i++) {
//width and margin setup of items
allBox[i].style.width = (containerWidth / items) - margin + "px";
allBox[i].style.margin = (margin / 2) + "px";
totalItemsWidth += containerWidth / items;
totalItems++;
}
//tumbnail-container width set up
container.style.width = totalItemsWidth + "px";
//slides controls number set up
const allSlides = Math.ceil(totalItems / items);
const ul = document.createElement("ul");
for (let i = 1; i <= allSlides; i++) {
const li = document.createElement("li");
li.id = i;
li.innerHTML = i;
li.setAttribute("onclick", "controlSlides(this)");
ul.appendChild(li);
}
controls.appendChild(ul);
}
window.onload = load();
* {
box-sizing: border-box;
}
.thumbnailslider {
width: 100%;
float: left;
overflow: hidden;
}
.thumbanilslider .thumbnailcontainer {
width: 100%;
float: left;
}
.thumbnailslider .artitem {
height: 175px;
background-color: grey;
line-height: 175px;
text-align: center;
font-size: 50px;
color: #ffffff;
float: left;
}
<div class="thumbnailslider">
<div class="thumbnailcontainer">
<div class="artitem"> 1 </div>
<div class="artitem"> 2 </div>
<div class="artitem"> 3 </div>
<div class="artitem"> 4 </div>
<div class="artitem"> 5 </div>
<div class="artitem"> 6 </div>
<div class="artitem"> 7 </div>
<div class="artitem"> 8 </div>
<div class="artitem"> 9 </div>
<div class="artitem"> 10 </div>
</div>
<!-- Control Slides -->
<div class="controls">
</div>
</div>
I am new to coding and programming and I have been following, on Youtube, a screen recording of a programmer making a responsive thumbnail slider using HTML, CSS, and Javascript.
I’ve gotten to a point where I am trying to get the control number of the slides to show on my page, but I continue to get this error message:
script.js:48 Uncaught TypeError: Cannot read property ‘appendChild’ of null at start (script.js:48) at load (script.js:23)at script.js:51 start @ script.js:48 load @ script.js:23 (anonymous) @ script.js:51″
Can someone tell me why this is happening? My code is below.
const controls = document.querySelector(".controls");
const container = document.querySelector(".thumbnailcontainer");
const allBox = container.children;
const containerWidth = container.offsetWidth;
const margin = 30;
var item = 0;
var totalItems = 0;
// item setup per slide
responsive =
[ { breakPoint: { width: 0, item: 1 }} // if width greater than 0 (1 will item show)
, { breakPoint: { width: 600, item: 2 }} // if width greater than 600 (2 will item show)
, { breakPoint: { width: 1000, item: 6 }} // if width greater than 1000 (4 will item show)
]
function load() {
for (let i = 0; i < responsive.length; i++) {
if (window.innerWidth > responsive[i].breakPoint.width) {
items = responsive[i].breakPoint.item
}
}
start();
}
function start() {
var totalItemsWidth = 0
for (let i = 0; i < allBox.length; i++) {
//width and margin setup of items
allBox[i].style.width = (containerWidth / items) - margin + "px";
allBox[i].style.margin = (margin / 2) + "px";
totalItemsWidth += containerWidth / items;
totalItems++;
}
//tumbnail-container width set up
container.style.width = totalItemsWidth + "px";
//slides controls number set up
const allSlides = Math.ceil(totalItems / items);
const ul = document.createElement("ul");
for (let i = 1; i <= allSlides; i++) {
const li = document.createElement("li");
li.id = i;
li.innerHTML = i;
li.setAttribute("onclick", "controlSlides(this)");
ul.appendChild(li);
}
controls.appendChild(ul);
}
window.onload = load();
* {
box-sizing: border-box;
}
.thumbnailslider {
width: 100%;
float: left;
overflow: hidden;
}
.thumbanilslider .thumbnailcontainer {
width: 100%;
float: left;
}
.thumbnailslider .artitem {
height: 175px;
background-color: grey;
line-height: 175px;
text-align: center;
font-size: 50px;
color: #ffffff;
float: left;
}
<div class="thumbnailslider">
<div class="thumbnailcontainer">
<div class="artitem"> 1 </div>
<div class="artitem"> 2 </div>
<div class="artitem"> 3 </div>
<div class="artitem"> 4 </div>
<div class="artitem"> 5 </div>
<div class="artitem"> 6 </div>
<div class="artitem"> 7 </div>
<div class="artitem"> 8 </div>
<div class="artitem"> 9 </div>
<div class="artitem"> 10 </div>
</div>
<!-- Control Slides -->
<div class="artcontrols">
</div>
</div>
@JaromandaX is correct. I’ve verified that if you change the selector to
