At http://blajeny.com I have:
jQuery('body').click(function(event_object)
{
spark(event_object.pageX, event_object.pageY);
});
function spark(x, y)
{
console.log('Spark called.');
var image_object = new Image();
image_object.onLoad = function()
{
image_object.style.position = 'absolute';
image_object.style.zIndex = 1;
image_object.style.top = y;
image_object.style.left = x;
}
image_object.src = '/img/spark.png';
}
The intended effect, at this stage, is to load an image at the X and Y where the user clicked. (I want to do other things as well, like animate it, but right now I'm trying to get the image to show up where the user clicked.)
The javaScript console shows that the handler is being called, however I am not seeing what I expect, a hazy blue circle immediately below and to the right of the point where the mouse was clicked.
What can/should I do differently so it loads a fresh image below and to the right of the clicked coordinates?
Thanks,
As far as I know, the onLoad should be onload
var image_object = document.createElement('img');
image_object.onload = function() { // Note the small onload
// your code
}
// Also, append the image_object to DOM
document.body.appendChild(image_object);
I don't see you appending the image to DOM that's probably why you're not seeing it
$('body').append($(image_object));
I agree, first create an element with the "img" tag, assign the src value to it, and append it to the current div (in this case its the body), like so
var imgTag = document.createElement("img");
imgTag.src = '/img/spark.png';
document.body.appendChild(imgTag);
Hope this helps.
You never append the image to the DOM, that's why you can't see it.
You can do
document.body.appendChild(image_object);
You must also replace onLoad by onload and specify the top and left position with an unit :
image_object.onload = function() {
image_object.style.position = 'absolute';
image_object.style.zIndex = 1;
image_object.style.top = '100px';
image_object.style.left = '100px';
}
Demonstration
Related
I'm creating a lazy load function and I want to append the image to the DOM after it has successfully loaded to create a smooth transition.
I have a function which loops through a list of elements with a specific class, which gradually gets smaller every time you scroll.
Once an image in that list is considered "visible" I add a class and it no longer get's evaluated by the function.
I get the SRC by a data attribute, and create a new Image();
I do some css prop manipulation and add the src after I add the onload function.
This works around 1/3 of the time, most images never fire the onload callback and aren't added to the DOM.
My script is as follows:
var lazyClass = 'js-lazyload';
function lazyLoader() {
//Sets an elements var that checks how many non-visible elements still exist
// This variable is reset every time lazyLoader() is called
var elements = document.querySelectorAll('.' + lazyClass + ':not(.js-lazyload--visible)');
//If there are no hidden elements left, end the function we don't need to proceed.
if (elements.length === 0) return;
//Loop through the elements array
//Only untoggled elements can be in this array because of the previous check
for(var i = elements.length; i--;) {
var lazyLoadElement = elements[i];
if (
lazyLoadElement.getBoundingClientRect().bottom <= window.innerHeight &&
lazyLoadElement.getBoundingClientRect().bottom > 0 ||
lazyLoadElement.getBoundingClientRect().top <= window.innerHeight &&
lazyLoadElement.getBoundingClientRect().top > 0)
{
//The element was considered visible, let's go!
lazyLoadElement.classList.add('js-lazyload--visible');
var imgData = lazyLoadElement.getAttribute('data-image'),
image = new Image(),
lazyStyle = window.getComputedStyle(lazyLoadElement);
if(lazyStyle.position !== 'relative'){
if(lazyStyle.position !== 'absolute'){
lazyLoadElement.style.position = 'relative';
}
}
image.onload = () => {
lazyLoadElement.classList.add('js-lazyload--loaded');
lazyLoadElement.insertBefore(image, lazyLoadElement.firstChild);
}
image.classList.add('js-lazyload__image')
image.style.position = 'absolute';
image.style.top = 0;
image.style.left = 0;
image.style.width = '100%';
image.style.height = '100%';
image.style.zIndex = '-1';
image.style.objectFit = 'cover';
image.src = imgData;
}
}
}
Here is a fiddle which shows the issue:
Elements red - not visible
Elements blue - visible, but no image
Elements green - visible with loaded image
https://jsfiddle.net/dalecarslaw/yumv6rft/
No jQuery Please.
The onload callback that you added is in fact getting fired properly.
The issue in this particular case is the fact that the variables declared using var are function scoped. This means that as your for loop finishes it's iteration, the lazyLoadElement variable is pointing to the same element for all the handlers that get fired with an onload handler.
Changing the declarations for lazyloadElement, imgData, image and lazyStyle from var to let will make the code work as intended.
I have an image - image1.png. When I click a button the first time, I want it to change to image2.png. When I click the button for a second time, I want it to change to another image, image3.png.
So far I've got it to change to image2 perfectly, was easy enough. I'm just stuck finding a way to change it a second time.
HTML:
<img id="image" src="image1.png"/>
<button onclick=changeImage()>Click me!</button>
JavaScript:
function changeImage(){
document.getElementById("image").src="image2.png";
}
I'm aware I can change the image source with HTML within the button code, but I believe it'll be cleaner with a JS function. I'm open to all solutions though.
You'll need a counter to bump up the image number. Just set the maxCounter variable to the highest image number you plan to use.
Also, note that this code removes the inline HTML event handler, which is a very outdated way of hooking HTML up to JavaScript. It is not recommended because it actually creates a global wrapper function around your callback code and doesn't follow the W3C DOM Level 2 event handling standards. It also doesn't follow the "separation of concerns" methodology for web development. It's must better to use .addEventListener to hook up your DOM elements to events.
// Wait until the document is fully loaded...,
window.addEventListener("load", function(){
// Now, it's safe to scan the DOM for the elements needed
var b = document.getElementById("btnChange");
var i = document.getElementById("image");
var imgCounter = 2; // Initial value to start with
var maxCounter = 3; // Maximum value used
// Wire the button up to a click event handler:
b.addEventListener("click", function(){
// If we haven't reached the last image yet...
if(imgCounter <= maxCounter){
i.src = "image" + imgCounter + ".png";
console.log(i.src);
imgCounter++;
}
});
}); // End of window.addEventListener()
<img id="image" src="image1.png">
<button id="btnChange">Click me!</button>
For achieve your scenario we have to use of counter flag to assign a next image. so we can go throw it.
We can make it more simple
var cnt=1;
function changeImage(){
cnt++;
document.getElementById("image").src= = "image" + cnt + ".png";
}
try this
function changeImage(){
var img = document.getElementById("image");
img.src = img.src == 'image1.png' ? "image2.png" : "image3.png";
}
Just use an if statement to determine what the image's source currently is, like so:
function changeImage(){
var imageSource = document.getElementById("image").src;
if (imageSource == "image1.png"){
imageSource = "image2.png";
}
else if (imageSource == "image2.png"){
imageSource = "image3.png";
}
else {
imageSource = "image1.png";
}
}
This should make the image rotate between 3 different image files (image1.png, image2.png and image3.png). Bear in mind this will only work if you have a finite number of image files that you want to rotate through, otherwise you'd be better off using counters.
Hope this helps.
Check the below code if you make it as a cyclic:
JS
var imgArray = ["image1.png", "image2.png", "image3.png"];
function changeImage(){
var img = document.getElementById("image").src.split("/"),
src = img[img.length-1];
idx = imgArray.indexOf(src);
if(idx == imgArray.length - 1) {
idx = 0;
}
else{
idx++;
}
document.getElementById("image").src = imgArray[idx];
}
html
<button onclick=changeImage();>Click me!</button>
function changeImage(){
document.getElementById("image").attr("src","image2.png");
}
I have created a webpage that basically displays 2 images side by side.
It has a "download" button, which triggers a vanilla Javascript function, which creates a <canvas> HTML element and concatenates the two images inside of it. It then creates a link with the base64-encoded result image as href and clicks on it:
<a download="image.png" id="dllink" href="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAABQAAAAMnCAYAAABhnf9DAAAgAElEQVR4nOzdR48kD3rn96j03pfv6qo21dVd3qT3JryP9Jll281..."></a>
Here is what the function I'm using looks like:
/**
* Create canvas, draw both images in it, create a link with the result
* image in base64 in the "href" field, append the link to the document,
* and click on it
*/
function saveImage() {
// Get left image
var imgLeft = new Image();
imgLeft.setAttribute('crossOrigin', 'anonymous');
imgLeft.src = "imgleft/" + idxImageShownLeft + ".jpg";
imgLeft.onload = function() {
// Once the left image is ready, get right image
var imgRight = new Image()
imgRight.setAttribute('crossOrigin', 'anonymous');
imgRight.src = "imgright/" + idxImageShownRight + ".jpg";
imgRight.onload = function() {
// Once the right image is ready, create the canvas
var canv = document.createElement("canvas");
var widthLeft = parseInt(imgLeft.width);
var widthRight = parseInt(imgRight.width);
var width = widthLeft + widthRight;
var height = imgLeft.height;
canv.setAttribute("width", width);
canv.setAttribute("height", height);
canv.setAttribute("id", "myCanvas");
canv.setAttribute('crossOrigin', 'anonymous');
var ctx = canv.getContext("2d");
// Draw both images in canvas
ctx.drawImage(imgLeft, 0, 0);
ctx.drawImage(imgRight, widthLeft, 0);
// Create PNG image out of the canvas
var img = canv.toDataURL("image/png");
// Create link element
var aHref = document.createElement('a');
aHref.href = img;
aHref.setAttribute("id", "dllink");
aHref.download = "image.png";
// Append link to document
var renderDiv = document.getElementById("render");
renderDiv.replaceChild(aHref, document.getElementById("dllink"));
// Click on link
aHref.click();
}
}
}
My problem is that this works fine on Firefox, but not on Chrome.
After a bit of investigating, I realized that by setting a breakpoint before the aHref.click(); line in Chrome, it worked fine. I think that it means that the aHref.click(); is called before the <a href="data:image/png;base64,...></a> is ready to be clicked, but I don't know for sure.
I couldn't find a duplicate of this topic. What keywords should I use just to be 100% sure?
Am I investigating in the right direction?
Is there an event I could rely on in order to call aHref.click(); only when it is ready?
You could wrap it in an init function that gets called when the window completes loading.
function init() {
aHref.click();
}
window.onload = init;
Its similar to the vanilla equivalent of jQuery's .ready() method.
aHref , document.getElementById("dllink") appear to be same element ? Though "dllink" has not yet been appended to document when .replaceChild called ?
Try substituting
renderDiv.appendChild(aHref);
for
renderDiv.replaceChild(aHref, document.getElementById("dllink"));
I want to write a code in which when you click on an image another image appears. After that when you click on the new image, another one appears, and so on.
I wrote this code which works for the first image. I can't figure out how to define the appeared images as inputs.
var i = 1
function addimage() {
var img = document.createElement("img");
img.src = "images/d" + i + ".jpg";
document.body.appendChild(img);
}
function counter() {
i = i + 1
}
<input type="image" src="images/d1.jpg" onclick="addimage(); counter();">
Attach an onclick function to the new image, with the same code as in your input tag:
var i = 1
function imageClick() {
if (! this.alreadyClicked)
{
addimage();
counter();
this.alreadyClicked = true;
}
}
function addimage() {
var img = document.createElement("img");
img.src = "http://placehold.it/" + (200 + i);
img.onclick = imageClick;
document.body.appendChild(img);
}
function counter() {
i = i + 1
}
<input type="image" src="http://placehold.it/200" onclick="imageClick();">
To add an event handler to an element, there are three methods; only use one of them:
=> With an HTML attribute. I wouldn't recommend this method because it mixes JS with HTML and isn't practical in the long run.
<img id="firstImage" src="something.png" onclick="myListener(event);" />
=> With the element's attribute in JS. This only works if you have a single event to bind to that element, so I avoid using it.
var firstImage = document.getElementById('firstImage');
firstImage.onclick = myListener;
=> By binding it with JavaScript. This method has been standardized and works in all browsers since IE9, so there's no reason not to use it anymore.
var firstImage = document.getElementById('firstImage');
firstImage.addEventListener("click", myListener);
Off course, myListener needs to be a function, and it will receive the event as its first argument.
In your case, you probably don't want to add another image when you click on any image that isn't currently the last. So when a user clicks on the last image, you want to add a new image and stop listening for clicks on the current one.
var i = 1;
function addNextImage(e) {
// remove the listener from the current image
e.target.removeEventListener("click", addNextImage);
// create a new image and bind the listener to it
var img = document.createElement("img");
img.src = "http://placehold.it/" + (200 + i);
img.addEventListener("click", addNextImage);
document.body.appendChild(img);
// increment the counter variable
i = i + 1;
}
var firstImage = document.getElementById("firstImage");
firstImage.addEventListener("click", addNextImage);
Try on JSFiddle
On a side note: while JavaScript does support omitting some semi-columns it's considered a better practice to put them, and it will avoid small mistakes.
I'm building a very simple lightbox script; when you click a button, the lightbox is created. When you click on the lightbox background, it is removed.
The first time you call the function it works just fine. Click button, lightbox shows, click lightbox, it disappears. However, if you try to click the button AGAIN, nothing happens - the div isn't called. No console errors or anything, don't know what the problem is.
JSFIDDLE http://jsfiddle.net/3fgTC/
CODE
function closeLightBox(){
document.body.removeChild(lightBox);
}
function createElem(){
var elem = "<div id='lightBox'></div>";
var bodyElem = document.body;
bodyElem.innerHTML = elem + bodyElem.innerHTML;
var lightBox = document.getElementById("lightBox");
lightBox.style.width = "100%";
lightBox.style.height = "800px";
lightBox.style.backgroundColor = "rgba(0,0,0,.5)";
lightBox.onclick = function(){
closeLightBox();
}
}
var button = document.getElementsByClassName("btn");
for (var i = 0; i<button.length; i++){
button[i].onclick = function(){
createElem();
}
}
Any ideas?
Don't prepend to innerHTML; that makes the browser re-parse the HTML and re-create every DOM element, losing event handlers in the process. Instead, use document.createElement:
var lightBox = document.createElement('div');
document.body.insertBefore(lightBox, document.body.firstChild);
Furthermore, inline closeLightBox:
lightBox.onclick = function() {
document.body.removeChild(lightBox);
}
Try it.