We Keep Coding

Propagation of Script

I probably should not be attempting this, but I have gotten so far and I don't want to give up now. I want to create my own Lightbox type script. I can create an absolute div with the class ligthbox and it covers the page. Then I create a img that is fixed and it animates when loading. The I also have nav arrows to move through the photos. All works accept when I click on the arrows it creates new close X and arrows. I don't understand because the is done through the animation function which is not attached to the arrow function.
I have added event.stopPropagation(); to the arrow function and the animate function but that did not work.
The function that initiates everything.
jQuery(".marks-lightbox img").click( function() {
var Img = jQuery(this),
cImg = Img.attr("src"),
allImg = jQuery(".marks-lightbox img");
//finding the current img from the available images
for(i=0; i < allImg.length; i++) {
if( jQuery(allImg[i]).attr("src") == Img.attr("src") ) {
lbImgCurrent = i;
}
}
makeLightBox()
});
function makeLightBox() {
var bodyHeight = jQuery("body").height(),
lightbox = jQuery("<div>").addClass("lightbox").css({"width":"100vw","height":bodyHeight}),
scrollTop = 72,
lbContainer = jQuery("<div>").addClass("lbContainer"),
lbImg = jQuery(".marks-lightbox img"),
imgSRC = jQuery(lbImg[lbImgCurrent]).attr("src"),
lbClose = jQuery("<span>").addClass("lb-close").text("X");
jQuery("body").prepend(lightbox);
lbContainer.appendTo(".lightbox");
jQuery('<img src="'+ imgSRC +'">').load(function() {
jQuery(this).appendTo(".lbContainer").css("display","none").addClass("lb-image");
var w = jQuery(".lb-image").width(),
h = jQuery(".lb-image").height(),
lbw = lightbox.width(),
margin = (lbw - w) /2;
jQuery(this).appendTo(".lightbox").css({"position":"fixed","display":"block","width":0,"height": 0}).animate({"top":scrollTop,"width":w,"height":h,"margin-left":margin, "margin-right":margin},1000,function(event){
var lbimg = jQuery(this),
lbH = lbimg.height() + 63,
lbLeft = lbimg.offset().left,
lbW = lbimg.width(),
larrow = jQuery("<div><</div>").addClass("left-arrow-lb lb-arrow"),
rarrow = jQuery("<div>></div>").addClass("right-arrow-lb lb-arrow");
larrow.appendTo("body").css({"position":"fixed","top":lbH/2,"left":lbLeft+18});
rarrow.appendTo("body").css({"position":"fixed","top":lbH/2,"left":lbLeft+lbW-90});;
lbClose.appendTo(".lightbox").css({"position":"fixed","top": lbH,"left": lbLeft+lbW - 18});
});
});
}
Here is the click function
jQuery("body").on("click",".left-arrow-lb", function() {
console.log(jQuery(this));
var lbImgLength = jQuery(".marks-lightbox img").length,
lbImg = jQuery(".marks-lightbox img");
lbImgCurrent = (lbImgCurrent < 1 ) ? lbImgLength : lbImgCurrent -1;
var imgSRC = jQuery(lbImg[lbImgCurrent]).attr("src");
console.log(imgSRC);
jQuery(".lb-image").attr("src",imgSRC);
});
Every click creates a load new img scr and animates the photo (unexpectedly) and creates new arrows and close x.

I found it was the on("load"... working every time an image was being loaded. So I created a var reload and set it to true. The in the on(load... function I said if not true return false. In the arrow functions set the reload to false. This prevented the on(load... working reloading.

Drawing an array of images on canvas in javascript [duplicate]

So I have been recently developing a site, The problem is the backgrounds for each page are images, and as a result, on slower connections (which is the case of some of the target audience) the images load progressivly as they are downloaded, to resolve this I am trying to make a preloading page that does the following :
Loads the Images
Once the loading is done, redirects the user to the requested page
<script type="text/javascript">
<!--//--><![CDATA[//><!--
var images = new Array()
var count=0;
function preload() {
for (i = 0; i < preload.arguments.length; i++) {
images[i] = new Image()
images[i].src = preload.arguments[i]
}
if(count==4) {
window.location = "index.html";
}
}
preload(
"backgrounds/bg1.jpg",
"backgrounds/bg2.jpg",
"backgrounds/bg3.jpg",
"backgrounds/bg4.jpg"
)
//--><!]]>
The problem is it redirects directly (I assume that it just starts the download of the image then directly adds one to the counter variable, quickly reaching 4 and not giving the image the time to download.
Any ideas how I can either make it signal me when the images have finished downloading, or only execute the redirect after it has done downloading the images ?

You need to wait for the load event. It's quite simple:
function preload(images, timeout, cb) {
var cbFired = false,
remaining = images.length,
timer = null;
function imageDone() {
remaining--;
if(remaining === 0 && !cbFired) {
cbFired = true;
clearTimeout(timer);
cb();
}
}
function timerExpired() {
if(cbFired)
return;
cbFired = true;
cb();
}
for(var i = 0; i < images.length; i++) {
var img = new Image();
img.onload = imageDone;
img.onerror = imageDone;
img.src = images[i];
}
timer = setTimeout(timerExpired, timeout);
}
You need to check a few things so that users don't get stuck:
You need to wait for both load and error so that the page doesn't get stuck if an image fails to load.
You should set a maximum timeout.
Also, in your code, i was a global variable (no var declaration).
Here's how to use it:
var images = [ "backgrounds/bg1.jpg",
"backgrounds/bg2.jpg",
"backgrounds/bg3.jpg",
"backgrounds/bg4.jpg"];
preload(images, 10000 /* 10s */, function () {
window.location = 'next_page';
});

Modify your preloader so that it binds to the "onload" event of the Image object and when all callbacks are fired it redirects (untested sample code below):
var images = new Array()
var count = 0;
function preload() {
var numImages = preload.arguments.length
for (i = 0; i < numImages; i++) {
images[i] = new Image();
images[i].onload = doneLoading; // See function below.
images[i].src = preload.arguments[i];
}
function doneLoading() {
if (++count >= numImages) {
window.location = "index.html";
}
}
}
preload(
"backgrounds/bg1.jpg",
"backgrounds/bg2.jpg",
"backgrounds/bg3.jpg",
"backgrounds/bg4.jpg"
)

How can I make this function loop with javascript?

function argsToArray(args) {
var r = []; for (var i = 0; i < args.length; i++)
r.push(args[i]);
return r;
}
argsToArray(document.getElementsByTagName('img')).forEach(function(img) {
img.src = img.src.split('VTlibOlte8YCb').join('X0X810D0' + Math.floor((Math.random()*10)+1));;
});
I tried adding setInterval(argsToArray,500); at the end but that seem to have broken things.
This is quite archaic and will probably crash the browser, but for this experiment it might just work.
function reloadPage()
{
location.reload();
}
setInterval(reloadPage,.5);

I assume from using native forEach that you're targeting IE9+, so instead of manually pushing the collection contents into an array you could just:
function argsToArray(args) {
return Array.prototype.slice.call(args)
}
The rest of the code looks perfectly workable, maybe there's something wrong with the split() or join() arguments. Please explain what are you trying to achieve here.
Adding setInterval(argsToArray,500) would just call your first function without any arguments, you should use an anonymous function or pass arguments into the setInterval/setTimeout function (see MDN).

So you want to do something like this?
window.onload=function() {
var imgs = document.images;
var tId = setInterval(function() {
for (var i=0;i<imgs.length;i++) {
var img = imgs[i];
var val = 'X0X810D0' + (Math.floor(Math.random()*10)+1);
img.src = img.src.replace(/VTlibOlte8YCb/g,val);
}
},1000);
}
which is designed replace the src of each image every second - but actually only once since there is no more VTlibOlte8YCb to replace after the first time
Here is one that does replace the value each time
Live Demo
window.onload=function() {
var imgs = document.images;
var oldVal = new RegExp(/VTlibOlte8YCb/g);
var val = 'X0X810D0' + (Math.floor(Math.random()*10)+1);
var tId = setInterval(function() {
for (var i=0;i<imgs.length;i++) {
var img = imgs[i];
val = 'X0X810D0' + (Math.floor(Math.random()*10)+1);
img.src = img.src.replace(oldVal,val);
oldVal = new RegExp("/"+val+"/g");
}
},200);
}

referencing function inside a for loop in js

I have the following code:
function fn_get_natural_dim(){
var width = this.width;
var height = this.height;
var ratiow = width/600;
var ratioh = height/300;
$("#output").append(img_name,",");
if(ratiow>=ratioh)
{
height = height/ratiow;
$(slide_image).css("width","600px");
$(slide_image).css("height",height);
var margin = (300-height)/2;
$(slide_image).css("margin-top",margin);
}
else
{
width = width/ratioh;
$(slide_image).css("width",width);
$(slide_image).css("height","300px");
var margin = (600-width)/2;
$(slide_image).css("margin-left",margin);
}
}
var max_count = $(".slider").children().length;
for(var count=1;count<=max_count;count++)
{
var count_string = count.toString();
var img_name = "img" + count_string;
var slide_image = document.getElementById(img_name);
var img = new Image();
img.onload = fn_get_natural_dim;
img.src = $(slide_image).attr("src");
}
});
For each image (i have three at the moment), im getting its natural dimensions so that i can calculate the margin necessary to fit a 600x300 div.
but i only works for the very last one, ie the third one.
in other words, in the #output, it shows "img3,img3,img3," (called by $("#output").append(img_name,",");)
how do i make it show "img1,img2,img3,"??

You can do this:
img.onload = (function(img_name, slide_image) {
return function() {fn_get_natural_dim(img_name, slide_image); };
})(img_name, slide_image);
and change fn_get_natural_dim to take the image name as a parameter:
function fn_get_natural_dim(img_name, slide_image) {
The above code captures each successive value of img_name in a closure variable.

Edit
As Barmar pointed out, this solution isn't exactly correct. I'll leave it up as it's a fairly common mistake and is important to note the difference between his solution and my own.
Pass img_name into your fn_get_natural_dim function:
function fn_get_natural_dim( img_name ) { ... }
Then call it like:
img.onload = function() { fn_get_natural_dim(img_name); };

Why doesn't this Javascript image object get added to the image array?

I've been trying to create a small HTML5-based example, but I've ran into some problems. I want to render a rock on a <canvas> but this Javascript object won't work properly.
function ImageData() {
this.image_names = ["rock1"];
this.images = new Array();
this.loadResources = function () {
for (var i = 0; i < this.image_names.length; i++) {
var img = new Image();
img.onload = (function (a) {
a.images[a.image_names[i]] = img;
console.log(a.images); //log is successful, image is in array
})(this);
img.src = "images/" + this.image_names[i] + ".png";
}
}
}
It's use is to be as follows:
var a = new ImageData();
a.loadResources();
var rock1_image = a.images["rock1"]; //the "rock1.png" image
If you try accessing the object via console, you'll see that there is no image in the image array, after being certain the image loaded. I can't figure out why it's not working. I've looked over it multiple times.
EDIT: Here is my final, working result:
function ImageData() {
this.image_names = ["rock1"];
this.images = new Array();
this.loadResources = function (callback) {
for (var i = 0; i < this.image_names.length; i++) {
var img = new Image();
img.onload = (function (a, i) {
return function() {
a.images[a.image_names[i]] = img;
if (i == (a.image_names.length - 1)) callback();
};
})(this, i);
img.src = "images/" + this.image_names[i] + ".png";
}
}
}

I would venture to say that you are attempting to access it before it is added to your array. I would suggest adding a callback or something to your loadResources method to make sure that it's there before you attempt to access it.
this.loadResources = function (callback) {
for (var i = 0; i < this.image_names.length; i++) {
var img = new Image();
img.onload = (function (a, i) {
return function() {
a.images[a.image_names[i]] = img;
console.log(a.images); //log is successful, image is in array
callback();
};
})(this, i);
img.src = "images/" + this.image_names[i] + ".png";
}
}
then
var a = new ImageData();
var rock1_image;
a.loadResources(function() {
rock1_image = a.images["rock1"];
// do whatever you need to do with the image in here.
});
Also, what #Igor mentions. I totally missed that. I adjusted the code above so you could keep your this scope without having to set it elsewhere.
Updated to take care of the i issue brought up by #RobD.

Remove (this) after onload handler definition. You are actually calling this function right away, assigning undefined (since it returns nothing) as img.onload value.

In the code:
> function ImageData() {
> this.image_names = ["rock1"];
> this.images = new Array();
> this.loadResources = function () {
> for (var i = 0; i < this.image_names.length; i++) {
> var img = new Image();
> img.onload = (function (a) {
This function will be run immediately and does not return a value, so undefined will be assigned. So no point in the assignment, just run the code.
> a.images[a.image_names[i]] = img;
Images is an array that is used as a plain object. Better to use a plain object then.
> console.log(a.images); //log is successful, image is in array
> })(this);
The outer this must be passed in because of the IIFE. Remove the IIFE and there is no requirement to pass this. And if a reference to the instance is stored in the function, it won't matter how the function is called (i.e. you won't have to set this in the call).
> img.src = "images/" + this.image_names[i] + ".png";
> }
> }
> }
You might want something like:
function ImageData() {
this.image_names = ['rock1'];
this.images = {};
imageData = this;
this.loadResources = function (callback) {
for (var i = 0; i < imageData.image_names.length; i++) {
var img = new Image();
imageData.images[a.image_names[i]] = img;
img.src = 'images/' + this.image_names[i] + '.png';
if (callback) {
img.onload = callback;
}
}
}
}
var a = new ImageData();
a.loadResources(function(){console.log('loaded: ' + this.src);}); // loaded: …
window.onload = function() {
document.body.appendChild(a.images.rock1); // image appears in document
}

I haven't tested your code yet, but I guess this is the problem:
You are trying to access your image before it was loaded. You can use callback event handler after it was load like:
var data = new ImageData();
data.loadResources(function(imgObj){
// imgObj is the newly load image here. Have fun with it now!
})