Develop Reference

jQuery - Run change function on load

In the wishlist ui function, I append items to the wishlist by checking the .wish-btn. I want to simulate items already added to the list so I need to run the function on load so that all of the items have been checked.
How do I run the function on load so that all of the items are:
Already checked
Appended to the list
var wish = {
items: []
};
var update_product = function(product) {};
$(function() {
//Add to wish
var addToWish = function(product, qty) {
qty = qty || 1;
var wish = getWish();
var indexOfId = wish.items.findIndex(x => x.id == product.id);
if (indexOfId === -1) {
wish.items.push({
id: product.id,
img: product.img,
name: product.name
});
$parent = $("#" + product.id).closest(".product");
$parent
.find(".wish-icon")
.addClass("active")
.attr("data-prefix", "fas");
} else {
wish.items[indexOfId].qty++;
wish.items[indexOfId].stock = Number(product.stock);
}
//Update popup wish
updateWish(wish);
};
//Remove from wish on id
var removeFromWish = function(id) {
var wish = getWish();
var wishIndex = wish.items.findIndex(x => x.id == id);
wish.items.splice(wishIndex, 1);
$parent = $("#" + id).closest(".product");
$parent
.find(".wish-icon")
.first()
.removeClass("active")
.attr("data-prefix", "far");
//Update popup wish
updateWish(wish);
};
var getProductValues = function(element) {
var productId = $(element)
.closest(".product")
.find(".item__title")
.attr("id");
var productImg = $(element)
.closest(".product")
.find(".item__img")
.attr("src");
var productName = $(element)
.closest(".product")
.find(".item__title")
.html();
return {
id: productId,
img: productImg,
name: productName
};
};
$(".my-wish-add").on("change", function() {
var product = getProductValues(this);
if ($(this).is(":checked")) {
addToWish({
id: product.id,
img: product.img,
name: product.name
});
} else {
removeFromWish(product.id);
}
});
//Update wish html to reflect changes
var updateWish = function(wish) {
//Add to shopping wish dropdown
$(".wishlist__items").html("");
for (var i = 0; i < wish.items.length; i++) {
$(".wishlist__items").append(
"<li class='wish__item'>" +
'<div class="wish__thumb">' +
"<img src='" +
wish.items[i].img +
"' />" +
"</div>" +
'<div class="wish__info">' +
'<div class="wish-name">' +
wish.items[i].name +
"</div>" +
"</div>" +
'<div class="wish__remove">' +
'<label class="wish__label">' +
'<input type="checkbox" id="my-wish-remove' +
i +
'" class="my-wish-remove" aria-hidden="true">' +
"<i class='fas fa-heart'></i>" +
"</div>" +
"</div>"
);
(function() {
var currentIndex = i;
$("#my-wish-remove" + currentIndex).on("change", function() {
$(this)
.closest("li")
.hide(400);
setTimeout(function() {
wish.items[currentIndex].stock = "";
update_product(wish.items[currentIndex]);
$("#" + wish.items[currentIndex].id).parents().find($(".wish-btn > input")).prop("checked", false);
removeFromWish(wish.items[currentIndex].id);
}, 400);
});
})();
}
};
//Get Wish
var getWish = function() {
var myWish = wish;
return myWish;
};
});
img {
width: 50px;
}
.my-wish-add {
font-family: "Font Awesome\ 5 Pro";
font-weight: 900;
}
.wish-btn {
position: relative;
}
.wish-btn input {
position: absolute;
opacity: 0;
top: 0;
left: 0;
right: 0;
bottom: 0;
cursor: pointer;
}
.wishlist__list {
right: 0;
width: 320px;
position: absolute;
padding: 20px;
}
<script src="https://pro.fontawesome.com/releases/v5.3.1/js/all.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div data-id="wishlist">
<div class="wishlist__list">
<ul class="wishlist__items">
</ul>
</div>
</div>
<div class='products'>
<div class="product">
<div id='headphones' class='item__title'>Item 1</div>
<img class="item__img" src="https://www.iconasys.com/wp-content/uploads/2017/06/360-Product-Photography-White-Background-Acrylic-Riser-08.jpg">
<label class="wish-btn">
<input type="checkbox" name="wish-check" class='my-wish-add'>
<i class="wish-icon far fa-heart"></i>
</input>
</label>
</div>
<div class="product">
<div class="items__cart">
<div id='backpack' class='item__title'>Item 2</div>
<img class="item__img" src="https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQoqpSgkG4AQDQOe33jI1NiW3GW2JSB-_v36aREsVyFQH55JFOJ">
<label class="wish-btn">
<input type="checkbox" name="wish-check" class='my-wish-add'>
<i class="wish-icon far fa-heart"></i>
</input>
</label>
</div>
</div>
<div class="product">
<div class="items__cart">
<div id='handbag' class='item__title'>Item 3</div>
<img class="item__img" src="https://qph.fs.quoracdn.net/main-qimg-de7d9680c4460296e461af9720a77d64">
<label class="wish-btn">
<input type="checkbox" name="wish-check" class='my-wish-add'>
<i class="wish-icon far fa-heart"></i>
</input>
</label>
</div>
</div>
</div>
`

Follow charlietfl's answer, then you will get an error:
TypeError: getWish is not a function
Then you have to move your change event handler to the bottom below getWish and updateWish function, because they need to be declared first to be used by the event handler.
var wish = {
items: []
};
var update_product = function(product) {};
$(function() {
//Add to wish
var addToWish = function(product, qty) {
qty = qty || 1;
var wish = getWish();
var indexOfId = wish.items.findIndex(x => x.id == product.id);
if (indexOfId === -1) {
wish.items.push({
id: product.id,
img: product.img,
name: product.name
});
$parent = $("#" + product.id).closest(".product");
$parent
.find(".wish-icon")
.addClass("active")
.attr("data-prefix", "fas");
} else {
wish.items[indexOfId].qty++;
wish.items[indexOfId].stock = Number(product.stock);
}
//Update popup wish
updateWish(wish);
};
//Remove from wish on id
var removeFromWish = function(id) {
var wish = getWish();
var wishIndex = wish.items.findIndex(x => x.id == id);
wish.items.splice(wishIndex, 1);
$parent = $("#" + id).closest(".product");
$parent
.find(".wish-icon")
.first()
.removeClass("active")
.attr("data-prefix", "far");
//Update popup wish
updateWish(wish);
};
var getProductValues = function(element) {
var productId = $(element)
.closest(".product")
.find(".item__title")
.attr("id");
var productImg = $(element)
.closest(".product")
.find(".item__img")
.attr("src");
var productName = $(element)
.closest(".product")
.find(".item__title")
.html();
return {
id: productId,
img: productImg,
name: productName
};
};
//Update wish html to reflect changes
var updateWish = function(wish) {
//Add to shopping wish dropdown
$(".wishlist__items").html("");
for (var i = 0; i < wish.items.length; i++) {
$(".wishlist__items").append(
"<li class='wish__item'>" +
'<div class="wish__thumb">' +
"<img src='" +
wish.items[i].img +
"' />" +
"</div>" +
'<div class="wish__info">' +
'<div class="wish-name">' +
wish.items[i].name +
"</div>" +
"</div>" +
'<div class="wish__remove">' +
'<label class="wish__label">' +
'<input type="checkbox" id="my-wish-remove' +
i +
'" class="my-wish-remove" aria-hidden="true">' +
"<i class='fas fa-heart'></i>" +
"</div>" +
"</div>"
);
(function() {
var currentIndex = i;
$("#my-wish-remove" + currentIndex).on("change", function() {
$(this)
.closest("li")
.hide(400);
setTimeout(function() {
wish.items[currentIndex].stock = "";
update_product(wish.items[currentIndex]);
$("#" + wish.items[currentIndex].id).parents().find($(".wish-btn > input")).prop("checked", false);
removeFromWish(wish.items[currentIndex].id);
}, 400);
});
})();
}
};
//Get Wish
var getWish = function() {
var myWish = wish;
return myWish;
};
// Move this block to the bottom after you have defined all functions
$(".my-wish-add").on("change", function() {
var product = getProductValues(this);
if ($(this).is(":checked")) {
addToWish({
id: product.id,
img: product.img,
name: product.name
});
} else {
removeFromWish(product.id);
}
}).prop('checked', true).change();
});
img {
width: 50px;
}
.my-wish-add {
font-family: "Font Awesome\ 5 Pro";
font-weight: 900;
}
.wish-btn {
position: relative;
}
.wish-btn input {
position: absolute;
opacity: 0;
top: 0;
left: 0;
right: 0;
bottom: 0;
cursor: pointer;
}
.wishlist__list {
right: 0;
width: 320px;
position: absolute;
padding: 20px;
}
<script src="https://pro.fontawesome.com/releases/v5.3.1/js/all.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div data-id="wishlist">
<div class="wishlist__list">
<ul class="wishlist__items">
</ul>
</div>
</div>
<div class='products'>
<div class="product">
<div id='headphones' class='item__title'>Item 1</div>
<img class="item__img" src="https://www.iconasys.com/wp-content/uploads/2017/06/360-Product-Photography-White-Background-Acrylic-Riser-08.jpg">
<label class="wish-btn">
<input type="checkbox" name="wish-check" class='my-wish-add'/>
<i class="wish-icon far fa-heart">click to wish</i>
</label>
</div>
<div class="product">
<div class="items__cart">
<div id='backpack' class='item__title'>Item 2</div>
<img class="item__img" src="https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQoqpSgkG4AQDQOe33jI1NiW3GW2JSB-_v36aREsVyFQH55JFOJ">
<label class="wish-btn">
<input type="checkbox" name="wish-check" class='my-wish-add'/>
<i class="wish-icon far fa-heart">click to wish</i>
</label>
</div>
</div>
<div class="product">
<div class="items__cart">
<div id='handbag' class='item__title'>Item 3</div>
<img class="item__img" src="https://qph.fs.quoracdn.net/main-qimg-de7d9680c4460296e461af9720a77d64">
<label class="wish-btn">
<input type="checkbox" name="wish-check" class='my-wish-add'/>
<i class="wish-icon far fa-heart">click to wish</i>
</label>
</div>
</div>
</div>

You can trigger a change right after you create a change event listener by chaining change() with no arguments to it.
Using prop('checked', true) will check them and you can chain that as well
$(selector).on('change', function(evt){
// do stuff when change occurs
// now check it and trigger change
}).prop('checked', true).change()

jQuery - hover works only on every 2nd div

I have a problem. I'm creating a divs from input form, but when I hover my mouse with .hover function, it works only on every second div element (first, third, 5th, 7th...). How do I solve that? What's wrong with JS function?
Thanks for answers.
JS:
$("#entryButton").click(function(){
event.preventDefault(); //stops refreshing
var query = $("#entry").val(); //string z inputa
if (query !== "") {
var trashButton = "<button class='trash'>DEL</button>"
var registry = "<div class='drag'>" + "<p>" + query + "</p>" + trashButton + "</div>"
$("#list").append(registry); //add div with query and ubbton
$("#list").sortable({
//axis: "y",
});
$(".drag").hover(function() {
$(this).toggleClass("mousehover")
});
$("#entry").val(""); //clear value
return false; //also stops refreshing
console.log(registry);
}
})
HTML:
<div class="container">
<form>
<input type="text" id="entry">
<button id="entryButton">button</button>
</form>
<ul id="list">
</ul>
</div>
CSS:
body {
font-size: 14px;
}
form {
float:right;
}
.container {
min-width:300px;
width:20%;
margin: 0 auto;
margin-top:5px;
}
.drag {
margin-top:5px;
background-color:lemonchiffon;
display:inline-flex;
width:100%;
}
.trash {
position:absolute;
margin-left:190px;
}
.mousehover {
opacity:0.5;
}

The problem is that you are adding the hover event multiple times. It is better to do it only once, using $(document).on().
$("#entryButton").click(function(){
event.preventDefault(); //stops refreshing
var query = $("#entry").val(); //string z inputa
if (query !== "") {
var trashButton = "<button class='trash'>DEL</button>"
var registry = "<div class='drag'>" + "<p>" + query + "</p>" + trashButton + "</div>"
$("#list").append(registry); //add div with query and ubbton
$("#list").sortable({
//axis: "y",
});
$("#entry").val(""); //clear value
return false; //also stops refreshing
console.log(registry);
}
});
$(document).on("mouseenter mouseleave", ".drag", function() {
$(this).toggleClass("mousehover");
});
body {
font-size: 14px;
}
form {
float:right;
}
.container {
min-width:300px;
width:20%;
margin: 0 auto;
margin-top:5px;
}
.drag {
margin-top:5px;
background-color:lemonchiffon;
display:inline-flex;
width:100%;
}
.trash {
position:absolute;
margin-left:190px;
}
.mousehover {
opacity:0.5;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jqueryui/1.12.1/jquery-ui.min.js"></script>
<div class="container">
<form>
<input type="text" id="entry">
<button id="entryButton">button</button>
</form>
<ul id="list">
</ul>
</div>

Here you go with a solution https://jsfiddle.net/wcu4w1mn/
$("#entryButton").click(function(){
event.preventDefault(); //stops refreshing
var query = $("#entry").val(); //string z inputa
if (query !== "") {
var trashButton = "<button class='trash'>DEL</button>"
var registry = "<div class='drag'>" + "<p>" + query + "</p>" + trashButton + "</div>"
$("#list").append(registry); //add div with query and ubbton
$("#list").sortable({
//axis: "y",
});
$(".drag").last().hover(function() {
$(this).toggleClass("mousehover")
});
$("#entry").val(""); //clear value
return false; //also stops refreshing
console.log(registry);
}
})
body {
font-size: 14px;
}
form {
float:right;
}
.container {
min-width:300px;
width:20%;
margin: 0 auto;
margin-top:5px;
}
.drag {
margin-top:5px;
background-color:lemonchiffon;
display:inline-flex;
width:100%;
}
.trash {
position:absolute;
margin-left:190px;
}
.mousehover {
opacity:0.5;
}
<link href="https://code.jquery.com/ui/1.12.1/themes/base/jquery-ui.css" rel="stylesheet"/>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://code.jquery.com/ui/1.12.1/jquery-ui.js"></script>
<div class="container">
<form>
<input type="text" id="entry">
<button id="entryButton">button</button>
</form>
<ul id="list">
</ul>
</div>
Only changed code
Add hover event to only last added element.
$(".drag").last().hover(function() {
$(this).toggleClass("mousehover")
});
Hope this will help you.

Converting javascript generated frames to divs

I have some old code that I am trying to convert to divs. It contains frames that have no target src, just JavaScript to generate a page.
Below is the code...
var editboxHTML =
'<html class="expand close">' +
'<head>' +
'<style type="text/css">' +
'.expand { width: 100%; height: 100%; }' +
'.close { border: none; margin: 0px; padding: 0px; }' +
'html,body { overflow: hidden; }' +
'<\/style>' +
'<\/head>' +
'<body class="expand close" onload="document.f.ta.focus(); document.f.ta.select();">' +
'<form class="expand close" name="f">' +
'<textarea class="expand close" name="ta" wrap="hard" spellcheck="false">' +
'<\/textarea>' +
'<\/form>' +
'<\/body>' +
'<\/html>';
var defaultStuff = 'This top frame is where you put your code.';
var extraStuff = '';
var old = '';
function init() {
window.editbox.document.write(editboxHTML);
window.editbox.document.close();
window.editbox.document.f.ta.value = defaultStuff;
update();
}
function update() {
var textarea = window.editbox.document.f.ta;
var d = dynamicframe.document;
if (old != textarea.value) {
old = textarea.value;
d.open();
d.write(old);
if (old.replace(/[\r\n]/g, '') == defaultStuff.replace(/[\r\n]/g, ''))
d.write(extraStuff);
d.close();
}
window.setTimeout(update, 150);
}
<frameset onload="init();" rows="50%,50%" resizable="no">
<frame name="editbox" src="javascript:'';">
<frame name="dynamicframe" src="javascript:'';">
</frameset>
This code has a user input box at the top to input HTML code into, and the bottom displays what that code would look like in a browser.
How would I manipulate this code to work with divs instead of frames, so I can include extra styling, and so that it is not fully depreciated in HTML5.
If your answer includes AJAX, please can you explain it as I am not familiar with that coding.
EDIT: If there is no div alternative, is there an iframe alternative?

Answer Updated
CSS Fixed
Error fixed
Jquery way:
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.4/jquery.min.js"></script>
<script>
var editboxHTML =
'<html class="expand close">' +
'<head>' +
'<style type="text/css">' +
'.expand { width: 100%; height: 50%; }' +
'.close { border: none; margin: 0px; padding: 0px; }' +
'html,body { overflow: hidden; }' +
'<\/style>' +
'<\/head>' +
'<body class="expand close">' +
'<form class="expand close" name="f">' +
'<textarea class="expand close" name="ta" wrap="hard" spellcheck="false">qweqwe' +
'<\/textarea>' +
'<\/form>' +
'<\/body>' +
'<\/html>';
var defaultStuff = 'This top frame is where you put your code.';
var extraStuff = '';
var old = '';
function init() {
$("#editbox").html(editboxHTML);
$("#editbox form[name='f'] [name='ta']").focus();
$("#editbox form[name='f'] [name='ta']").val(defaultStuff);
update();
}
function update() {
var textarea = $("#editbox form[name='f'] [name='ta']");
var d = $("#dynamicframe");
if (old != textarea.val()) {
old = textarea.val();
if (old != undefined){
d.html(old);
if (old.replace(/[\r\n]/g, '') == defaultStuff.replace(/[\r\n]/g, '')){
d.append(extraStuff);
}
}
else{
d.html("old undefined");
}
}
setTimeout("update()", 150);
}
</script>
<button onclick="init()">EDIT</button>
<div id="editbox"></div>
<div id="dynamicframe"></div>

you can just create one div tag with id say <div id='editbox' /> and add one line code in your update function document.getElementById("editbox").innerHTML=editboxHTML;

Unable to store permanently the id of dragged item

I am working on a project in which i had to store the the 3ID's of drop item in 3 textbox. but when i dragg and drop either one it stores it's id but when i drop the second item it stores it's ID but remove the ID of first from the textbox.
code
function dropItems(idOfDraggedItem, targetId, x, y) {
var targetObj = document.getElementById(targetId);
var subDivs = targetObj.getElementsByTagName('DIV');
if(subDivs.length>0 && targetId!='body')return;
var sourceObj = document.getElementById(idOfDraggedItem);
var numericIdTarget = targetId.replace(/[^0-9]/gi,'')/1;
var numericIdSource = idOfDraggedItem.replace(/[^0-9]/gi,'')/1;
if (numericIdTarget == '101') {
document.getElementById('txt1').value = numericIdSource;
} else {
document.getElementById('txt1').value = "";
}
if (numericIdTarget == '102') {
document.getElementById('txt2').value = numericIdSource;
} else {
document.getElementById('txt2').value = "";
}
if (numericIdTarget == '103') {
document.getElementById('txt3').value = numericIdSource;
} else {
document.getElementById('txt3').value = "";
}
var fn = "Feeling1:-" + document.getElementById('txt1').value + ", Feeling2:-" + document.getElementById('txt2').value + ", Feeling3:-" + document.getElementById('txt3').value + "";
document.getElementById('txt4').value = fn;
if (numericIdTarget - numericIdSource == 100) {
sourceObj.style.backgroundColor = '';
} else {
sourceObj.style.backgroundColor = '';
}
if (targetId == 'body') {
targetObj = targetObj.getElementsByTagName('DIV')[0];
}
targetObj.appendChild(sourceObj);
}
Initialization (from comments)
$(document).ready(function(e) {
var inp1=$("#txt1");
var inp2=$("#txt2");
var inp3=$("#txt3");
$("#bttn").click(function(){
if(inp1.val()=="" && (inp2.val()!="" || inp3.val()!="")) {
alert("Provide answer in consecutive manner");
} else if((inp1.val()=="" || inp2.val()=="") && inp3.val()!="" ) {
alert("Provide answer in consecutive manner");
} else {
alert("Submit");
}
});
})

I like to use jquery's built in draggable/droppable to acquire id's maybe this will help you with your current situation.
<!DOCTYPE HTML>
<html>
<head>
<title>Test Page</title>
<script src="//code.jquery.com/jquery-1.10.2.js"></script>
<script src="//code.jquery.com/ui/1.11.4/jquery-ui.js"></script>
<script>
$(function() {
$( ".draggable" ).draggable();
$( ".droppable" ).droppable({
drop: function( event, ui ) {
var id = $( this ).attr("id");
var container = ui.draggable.attr("id");
alert(id + " " + container);
}
});
});
</script>
<style>
.draggable{
width: 100px;
height: 50px;
border: 1px black solid;
margin: 0.5em;
}
.droppable{
width: 100px;
height: 50px;
border: 1px black solid;
margin: 0.5em;
}
</style>
</head>
<body>
<div id="draggable1" class="draggable">
<p>Drag me to my target</p>
</div>
<div id="draggable2" class="draggable">
<p>Drag me to my target</p>
</div>
<div id="draggable3" class="draggable">
<p>Drag me to my target</p>
</div>
<div style="height: 25px;"></div>
<div id="droppable1" class="droppable">
<p>Drop here</p>
</div>
<div id="droppable2" class="droppable">
<p>Drop here</p>
</div>
</body>
</html>

HTML/JavaScript: Why don't my buttons work?

I wrote a code for a 5 image slideshow and the NEXT and PREVIOUS buttons are supposed to take you to the next and previous slide but nothing happens when i press them. Can anyone help me out? some more detail some more detail some more detail some more detail
var slideShow = [];
function newImage(source, caption) {
var pic = new Object();
pic.src = source;
pic.cap = caption;
return pic;
}
slideshow[0] = newImage("slideshow1.jpg", "The Happy Cat");
slideshow[1] = newImage("slideshow2.jpg", "The Tube Cat");
slideshow[2] = newImage("slideshow3.jpg", "The Chubby Cat");
slideshow[3] = newImage("slideshow4.jpg", "if I fits I sits ");
slideshow[4] = newImage("slideshow5.jpg", "The classic Nicolas Cage");
var i = 0;
function nextPic() {
i = (i + 1);
if (i == 5)
i = 0;
document.getElementById("picture").innerHTML = '<img src= ' +
slideshow[i].src + ' id="images" height="100%"' +
' alt="my picture"> <p>' + slideshow[i].cap + '</p>';
}
function prevPic() {
if (i == -1)
i = 4;
else
i = (i - 1);
document.getElementById("picture").innerHTML = '<img src= ' +
slideshow[i].src + ' id="images" height="100%"' +
' alt="my picture"> <p>' + slideshow[i].cap + '</p>';
}
#picture {
width: 200px;
margin-left: 50;
margin-right: auto;
}
div.buttons {
width: 200px;
margin-left: auto;
margin-right: auto;
}
div.info {
width: 500px;
text-align: center;
margin-left: auto;
margin-right: auto;
border: 3px solid purple;
}
button {
font-size: 12px;
}
button.left {
auto;
margin-right: 418px;
}
p {
text-align: center;
}
<h3>Project 2: Slide Show</h3>
<h4>I do not own any of the following pictures</h6>
<h4>All pictures acquired online, unknown owners</h4>
<br />
<div id="picture">
<img src="slideshow1.jpg" id="images" alt="my picture" height="200 px">
<p>The Happy Cat</p>
</div>
<div class="buttons">
<button class="left" onClick="prevPic()">PREVIOUS</button>
<button onClick="nextPic()">NEXT</button>
</div>

1) Typo in slideShow
2)Not related but you cannot have duplicate id instead use class
var slideshow = [];
function newImage(source, caption) {
var pic = new Object();
pic.src = source;
pic.cap = caption;
return pic;
}
slideshow[0] = newImage("slideshow1.jpg", "The Happy Cat");
slideshow[1] = newImage("slideshow2.jpg", "The Tube Cat");
slideshow[2] = newImage("slideshow3.jpg", "The Chubby Cat");
slideshow[3] = newImage("slideshow4.jpg", "if I fits I sits ");
slideshow[4] = newImage("slideshow5.jpg", "The classic Nicolas Cage");
var i = 0;
function nextPic() {
i = (i + 1);
if (i == 5)
i = 0;
document.getElementById("picture").innerHTML = '<img src= ' +
slideshow[i].src + ' class="images" height="100%"' +
' alt="my picture"> <p>' + slideshow[i].cap + '</p>';
}
function prevPic() {
if (i == -1)
i = 4;
else
i = (i - 1);
document.getElementById("picture").innerHTML = '<img src= ' +
slideshow[i].src + ' class="images" height="100%"' +
' alt="my picture"> <p>' + slideshow[i].cap + '</p>';
}
<h3> Project 2: Slide Show </h3>
<h4> I do not own any of the following pictures </h6>
<h4> All pictures acquired online, unknown owners </h4>
<br />
<div id="picture">
<img src="slideshow1.jpg" class="images" alt="my picture" height="200 px">
<p>The Happy Cat</p>
</div>
<div class="buttons">
<button class="left" onClick="prevPic()">PREVIOUS</button>
<button onClick="nextPic()">NEXT</button>
</div>

You declaring var slideShow = []; array, however later you are populating slideshow with the code:
slideshow[0] = newImage("slideshow1.jpg","The Happy Cat");
which throws ReferenceError because you can't set property of the undefined.

Use var slideshow = [] instead of var slideShow = []