I'm trying to learn JS and this is my little app.
Every time I press the "INSTANTIATE" button, it instantiates a tomatoe.png in my <div>.
When the user reloads the page, the tomatoe.png should appear as many times as they've pressed the "INSTANTIATE" button.
This is the code. For this purpose, I created a variable (i), and it increments on every button press.
I planned to save this variable into localStorage, and when the page gets reloaded, I want to call a loop function that instantiates the tomatoe.png i times.
function popUp() {
var img = document.createElement("img");
img.src = "tomato.png";
var src = document.getElementById("header");
src.appendChild(img);
i++;
localStorage.setItem("apples", i);
}
<button onclick="popUp()">INSTANTIATE</button>
<div id="header"></div>
So, when the user reloads the page, as many tomatoes should appear as many times they've pressed the button.
I think I have to use a loop, but I don't know how.
Just get the item in localStorage and loop until it reaches 0, creating a new image each time (localStorage don't works in StackOverflow snippets here because of security reasons, but you get the point).
var i = 0;
function popUp() {
newImage();
i++;
localStorage.setItem("apples", i);
}
function newImage() {
var img = document.createElement("img");
img.src = "tomato.png";
var src = document.getElementById("header");
src.appendChild(img);
}
var oldi = Number(localStorage.getItem("apples"));
while (oldi > 0) {
oldi--;
newImage();
}
<button onclick="popUp()">INSTANTIATE</button>
<div id="header"></div>
First of all, you have to declare i outside your function (in case you haven't done it already) and give it a value of zero, if it isn't exist in the Local Storage:
let i = localStorage.getItem("apples") || 0;
Then, create a loop, that loops i times:
for(let n = 0; n < i; n++){}
And finally, just create tomatoes:
const img = document.createElement("img");
img.src = "tomato.png";
const src = document.getElementById("header");
src.appendChild(img);
So, the full code should look like this:
document.addEventListener('DOMContentLoaded', function(){
function popUp() {
createTomato()
i++;
localStorage.setItem("apples", i);
}
function createTomato() {
const img = document.createElement("img");
img.src = "tomato.png";
const src = document.getElementById("header");
src.appendChild(img);
}
document.getElementById("instantiate").addEventListener("click", popUp)
let i = localStorage.getItem("apples") || 0;
for (let n = 0; n < i; n++) createTomato();
})
<button id="instantiate">INSTANTIATE</button>
<div id="header"></div>
Try it on codepen.io
Related
My code is running well...
but there is one thing I can't solve:
when I mouseover the image the loop starts well, but on subsequent mouseovers it starts changing faster and faster...
var Image = new Array("//placehold.it/400x180/?text=Welcome",
"//placehold.it/400x180/?text=To",
"//placehold.it/400x180/?text=My",
"//placehold.it/400x180/?text=Web+page",
"//placehold.it/400x180/?text=INPHP");
var Image_Number=0;
var Image_Length= Image.length;
function change_image(num){
Image_Number = Image_Number + num;
if(Image_Number > Image_Length)
Image_Number = 0;
if(Image_Number < Image_Length)
document.slideshow.src = Image[Image_Number];
return false;
Image_Number = Image_Length;
}
function auto () {
setInterval("change_image(1)", 1000);
}
<img src="//placehold.it/400x180/?text=Welcome" name="slideshow" onmouseover="auto()" />
On every mouseover you're reassigning a brand-new-interval™ resulting in multiple functions running at the same time.
name on IMG tag is an obsolete HTML5 attribute - See also img tag # W3.org
"change_image(1)" ...strings inside setInterval or setTimeout tigger eval. Which is bad. The real function name should be used instead: setInterval(functionName, ms)
You're not managing well the argument num
You cannot have code after a return statement
Use the mouseenter event (instead of mouseover)
and many more errors....
Here's a remake:
var images = [
"//placehold.it/400x180/?text=Welcome",
"//placehold.it/400x180/?text=To",
"//placehold.it/400x180/?text=My",
"//placehold.it/400x180/?text=Web+page",
"//placehold.it/400x180/?text=INPHP"
];
var c = 0; // c as Counter ya?
var tot = images.length;
var angryCat = false;
// Preload! Make sure all images are in tha house
for(var i=0; i<tot; i++) {
var im = new Image();
im.src= images[i];
}
function changeImage() {
document.slideshow.src = images[++c%tot];
}
function auto() {
if(angryCat) return; // No more mouse enter
angryCat = true;
setInterval(changeImage, 1000);
}
<img src="//placehold.it/400x180/?text=Welcome" name="slideshow" onmouseenter="auto()" />
The increment and loop is achieved using ++c % tot
The angryCat boolean flag helps to know it the auto() already started (mouse was there!), in that case it will return; (exit) the function preventing the creation of additional overlapping intervals on subsequent mouseenter (which was your main issue).
Additionally, I'd suggest to keep your JS away from HTML, so instead of the JS attribute event
onmouseenter="auto()"
assign an ID to your image id="myimage" and use JS:
document.getElementById("myimage").addEventListener("mouseenter", auto, false);
I have a table with 3 columns that show cards back, like this, so when a I press on card, an alert show me his number, but I don't know how show the number, I tried with href and onClick but I haven't success
The html
<table id="gallery">
</table>
<script>generateTable3col();</script>
The js
function generateTable3col(){
var cards = [5,1,8,3,2,4,6];
var rows = cards.length/3;
var columns = 3;
var rowNode, columnNode, link, img;
var table = document.getElementById("gallery")
var image = "backcard.png"
for (var r=0;r<rows;r++){
rowNode = document.createElement("tr");
rowNode.style = "width:33%;";
table.appendChild(rowNode);
for(var c=0;c<columns; c++){
columnNode =document.createElement("td");
columnNode = table.appendChild(columnNode);
link = document.createElement("a");
link.setAttribute("hideNumber", cards[1*r+c]);
//here I don't know how do
link.href = "javascript:showCard(this)" //this is window object
link.onclick = showCard(this); //execute when call the loop not when click
img = document.createElement("img");
img.style = "width: 100%;"
img.src = image;
link.appendChild(img);
columnNode.appendChild(link);
}
}
}
//How?
function showCard(element){
alert("card is: " + element.getAttribute("hideNumber")); //element is object window, not <a> element
}
Instead of this line:
link.onclick = showCard(this);
Use this:
link.onclick = function() { showCard(this); };
The difference here is that in the first case, showCard(this); is executed right away. While in the second case, you're assigning a function to onclick that will only get executed once the click occurs.
FOr some reason my code is not executing properly. i am trying to program a slideshow with javascript. Im using a for loop to pull and populate the src files from a created array and change the pic every 3 seconds. THe page loads and the first pic is present but when the interval occurs the first pic dissapears and nothing falls in its place. What am I doing wrong?
<img name="mainSlide" id="mainSlide" src="images/mainPagePhotos/facebook-20131027-180258.png" alt="">
var mainSlidePics = ("facebook-20131027-180258.png","IMG_9694116683469.jpg","IMG_28452769990897.jpg");
window.onload = setInterval("mainSlide();", 3000);
function mainSlide() {
for(i=0; i<mainSlidePics.length; i++ ) {
document.images.mainSlide.src = "images/mainPagePhotos/" + mainSlidePics[i];
}
}
Have you tried getting the Id first?
var mainSlide = document.getElementById("mainSlide");
mainSlide.src = "images/mainPagePhotos/" + mainSlidePics[i];
also a forloop is a loop that finishes its loops even in one call.
try
var i = 0;
window.onload = setInterval("mainSlide(i);", 3000);
mainSlide(int j){
mainSlide.src = "images/mainPagePhotos/" + mainSlidePics[i];
setInterval("mainSlide(j++);", 3000);
}
First you have to correctly declare the array.
Then you have to move the counter variable outside the function triggered by setInterval.
Then pass the reference of the function to setInterval.
<img name="mainSlide" id="mainSlide" src="images/mainPagePhotos/facebook-20131027-180258.png" alt="">
<script type="text/javascript">
var mainSlidePics = ["facebook-20131027-180258.png","IMG_9694116683469.jpg","IMG_28452769990897.jpg"];
var position = 0;
function changePic() {
position = (position+1) % mainSlidePics.length;
document.images.mainSlide.src = "images/mainPagePhotos/" + mainSlidePics[position];
}
window.onload = function() {
setInterval(changePic, 3000);
};
</script>
I am calling this function on add button from my PHTML. On click of add button I want to show image of selected fruit in <div>.
function moveoutid()
{
var sda = document.getElementById('availableFruits');
var len = sda.length;
var sda1 = document.getElementById('orderFruits');
for(var j=0; j<len; j++)
{
if(sda[j].selected)
{
alert(baseUrl+"/img/"+sda.options[j].value+".jpg");
var img1=document.createElement('img').src=baseUrl+"/img/"+sda.options[j].value+".jpg";
var di=document.getElementById('d');
di.appendChild(img1);
var tmp = sda.options[j].text;
var tmp1 = sda.options[j].value;
sda.remove(j);
j--;
var y=document.createElement('option');
y.text=tmp1;
try
{
sda1.add(y,null);
}
catch(ex)
{
sda1.add(y);
}
}
}
}
In this code I have created <img> tag and passing image path to src, to show selected image on web page. It is correctly taking path of images but it is not appending <img> tag and not displaying image on web page.
Your problem is, most likely, in this line:
var img1=document.createElement('img').src=baseUrl+"/img/"+sda.options[j].value+".jpg";
This creates an element, assigns the src property to it and then assigns the value of this src property to variable img1. Instead, you should do this in two lines:
var img1 = document.createElement('img');
img1.src = baseUrl+"/img/"+sda.options[j].value+".jpg";
So far I created an array with 11 images, initialized the counter, created a function, created a for loop but here is where I get lost. I looked at examples and tutorial on the internet and I can see the code is seeming simple but I'm not getting something basic here. I don't actually understand how to call the index for the images. Any suggestions. Here is the code.
<script type="text/javascript">
var hammer=new Array("jackhammer0.gif",
"jackhammer1.gif",
"jackhammer2.gif",
"jackhammer3.gif",
"jackhammer4.gif",
"jackhammer5.gif",
"jackhammer6.gif",
"jackhammer7.gif",
"jackhammer8.gif",
"jackhammer9.gif",
"jackhammer10.gif")
var curHammer=0;
var numImg = 11;
function getHammer() {
for (i = 0; i < hammer.length; i++)
{
if (curHammer < hammer.length - 1) {
curHammer = curHammer +1;
hammer[i] = new Image();
hammer[i].src="poses/jackhammer" +(i+1) + ".gif";
var nextHammer = curHammer + 1;
nextHammer=0;
{
}
}
}
}
setTimeout("getHammer()", 5000);
</script>
</head>
<body onload = "getHammer()";>
<img id="jack" name="jack" src = "poses/jackhammer0.gif" width= "100" height ="113" alt = "Man and Jackhammer" /><br/>
<button id="jack" name="jack" onclick="getHammer()">Press button</button>
Following on what Paul, said, here's an example of what should work:
var hammer=["jackhammer0.gif","jackhammer1.gif","jackhammer2.gif","jackhammer3.gif",
"jackhammer4.gif","jackhammer5.gif","jackhammer6.gif","jackhammer7.gif",
"jackhammer8.gif","jackhammer9.gif","jackhammer10.gif"];
var curHammer=0;
function getHammer() {
if (curHammer < hammer.length) {
document.getElementById("jack").src= "poses/" + hammer[curHammer];
curHammer = curHammer + 1;
}
}
setTimeout("getHammer()", 5000);
The big missing element is that you need to call getElementById("jack") to get a reference to the DOM Image so that you can change it's source. If you're using jQuery or most other JS frameworks, just type $("#jack") to accomplish the same.
I don't understand the need for the for loop at all, just increment the index value [curHammer] each time you click, and reset if it passes your max index length (in this case 11).
Pseudo-Code:
currentHammer = -1
hammers = [ "a1.jpg", "a2.jpg", "a3.jpg"]
getHammer()
{
currentHammer = currentHammer + 1;
if(currentHammer > 2)
currentHammer = 0;
image.src = hammers[currentHammer];
}
a) are you just trying to show an animated gif? If so, why not use Adobe's Fireworks and merge all those gifs into a single gif?
b) you know that the way you have it the display is going to go crazy overwriting the gif in a circle right?
c) you might want to put a delay (or not). If so, make the load new gif a separate function and set a timeout to it (or an interval).
Also, you are being redundant. How about just changing the src for the image being displayed?:
var jackHammer = new Array();
for (var i=0;i<11;i++) { //pre-loading the images
jackHammer[i] = new image();
jackHammer[i].src = '/poses/jackHammer'+i.toString()+'.gif';
} //remember that "poses" without the "/" will only work if that folder is under the current called page.
for (var i=0;i<11;i++) { //updating the image on
document.getElementById('jhPoses').src = jackHammer[i].src;
}
on the document itself,
< img id='jhPoses' src='1-pixel-transparent.gif' width='x' height='y' alt='poses' border='0' />