If I write the html:
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<h1 id="message">
</h1>
and the JS:
messages = ["Here", "are", "some", "messages."]
$(function() {
for (var i = 0; i < messages.length; i++) {
$('#message').html(messages[i]).delay(1000);
}
});
and load the page, I expect to see each string in the array show up with a delay in between. However, all I see is "messages." appear. It seems that the for loop iterates immediately through each value in the array before performing any delay.
I have seen another method for getting the desired visual result (How can I change text after time using jQuery?), but I would like to know why the earlier method does not work. What is going on when this code is executed?
This is how i would delay my message changing.
function delayLoop(delay, messages) {
var time = 100;
$(messages).each(function(k, $this) {
setTimeout(function()
{
$("#message").html($this);
}, time)
time += delay;
});
}
delayLoop(1000, ["Here", "are", "some", "messages."]);
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="message">
</div>
All I did was for each message delay by an additional delay time.
It works in async mode so its not ui blocking and the messages will display a second after one another.
EDIT:
Removed the .delay from the .html it is redundant.
Note that jQuery's delay is specifically for effects; methods like html do not use the effects queue and are therefore not affected by delay.
This is a problem better solved with JavaScript's native setTimeout function. There are many ways to do this; in fact, you don't even need jQuery!
let messages = ["Here", "are", "some", "messages."];
let delay = 1000;
let header = document.getElementById("message");
messages.forEach(function(message, i) {
setTimeout(function() {
header.innerText = message;
}, delay * i);
});
<h1 id="message" />
You would need something along the lines of
$(function() {
for (var i = 0; i < messages.length) {
var done=false;
$('#message').html(messages[i]).delay(1000).queue(function(){
done=true;
$(this).dequeue();
});
if(done==true){
i++;
}
}
});
Thank you for the answers and comments--very helpful.
I also found this post helpful: Node.js synchronous loop, and from it wrote this (which also works):
function changeText() {
var msg = messages.shift();
$('#message').html(msg).show(0).delay(1000).hide(0, function() {
if (messages.length > 0) {
changeText();
}
});
}
(I used .show and .hide because without them only one of the array values appeared. I'm not sure why that is, but that's a question for another time.)
Related
I've been reading about the single-thread nature of javascript and how the UI will not update until the code is complete (eg. this question). The responses to that question mainly explained how the code executes, but didn't provide a real viable solution outside of some "hacky" timers.
I'm wondering if there is a good solution, that may include promises, or .then() functionality that will "paint" the UI prior to javascript execution.
The following is a specific example: http://jsfiddle.net/zbtsd12k/. In this example I would expect the "Change Color" to change immediately, prior to the calculation being run.
WARNING: My example includes a for-loop of one billion iterations (which took < 2 seconds on my machine) and may freeze your computer for a bit.
Any help would be appreciated.
A few changes
Added a setTimeout around the "logic" so that the DOM has a chance to redraw
Broke apart the then(makeCalculations()) line because #1 updateClass() does not return a promise and #2 then(methodCall()) would execute the methodCall immediately because you put () on the end of it.
function updateClass(element, newClass) {
element.addClass(newClass);
return true;
};
function makeCalculations() {
$("p").text("Running...");
setTimeout(function() {
var x = 0;
for (var i = 0; i < 1000000000; i++) {
x += i;
}
$("p").html("Done!" + "<br />" + "x = " + x);
}, 10);
}
$(function() {
$("button").click(function() {
updateClass($("span"), "purple");
makeCalculations();
});
});
.purple {
color: purple;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<span>Change Color</span>
<br>
<button>Click Me</button>
<p>Click the button</p>
I am getting an issue with a large amount of processing causing the non-responsive script error in IE8 (and no, I cannot make the users use a better browser).
I then read that it should be possible to split up the tasks and cede control back to the browser in between different parts of the validation. So I decided to make a simple example based on some code I found to figure out where the breaking points are. The real code is doing lots of jquery validationengine processing.
I tried to use jsFiddle but I can't get jsFiddle to run in IE8. Bummer. So, I'll have to share inline here.
When I first load it, it seems to work just fine. I push the button and both functions finish without a problem. However, subsequent pushes causes an unresponsive script error. I've played around with the number of loops in my simulated work function. Much more than 1.25 million loops and it dies with unresponsive script.
Shouldn't separate calls to the onClick start the non-responsive counter anew? What am I missing here?
<html>
<head>
<script>
var progress = null;
var goButton = null;
window.onload = function() {
progress = document.getElementById("progress");
goButton = document.getElementById("goButton");
}
function runLongScript(){
// clear status
progress.value = "";
goButton.disabled=true;
var tasks = [function1, function2];
multistep(tasks,null,function() {goButton.disabled=false;});
}
function function1() {
var result = 0;
var i = 1250000;
for (;i>0; i--) {
result = result + 1;
}
progress.value = progress.value + "f1 end ";
}
function function2() {
var result = 0;
var i = 1250000;
for (;i>0; i--) {
result = result + 1;
}
progress.value = progress.value + "f2 end";
}
function multistep(tasks, args, callback){
var tasksClone = tasks.slice(0); //clone the array
setTimeout(function(){
//execute the next task
var task = tasksClone.shift();
task.apply(null, args || []);
//determine if there's more
if (tasksClone.length > 0){
setTimeout(function () {
multistep(tasksClone, args, callback);
}, 100);
} else {
callback();
}
}, 100);
}
</script>
</head>
<body>
<p><input type="button" id="goButton" onClick="runLongScript();" value="Run Long Script" /></p>
<input type="text" id="progress" />
</body>
</html>
You're never calling clearTimeout() to remove the one currently running when the button has been pressed already. Add an if statement before you start another setTimeout and check to see if one is already running, clear it if it is, and then continue. Here's a link that should help you if you have any questions: https://developer.mozilla.org/en-US/docs/Web/API/window.clearTimeout
I created an image slider that ends on one image, but now I'd like to take it a step further and make it loop.
Here is my code in the head tag
<style>
#picOne, #picTwo, #picThree, #picFour, #picFive{
position:absolute;
display: none;
}
#pics {
width:500px;
height:332px;
}
</style>
<script src="http://code.jquery.com/jquery-1.4.4.min.js" type="text/javascript"></script>
<script type="text/javascript">
$(document).ready(function() {
$('#picOne').fadeIn(1500).delay(3500).fadeOut(1500);
$('#picTwo').delay(5000).fadeIn(1500).delay(3500).fadeOut(1500);
$('#picThree').delay(10000).fadeIn(1500).delay(3500).fadeOut(1500);
$('#picFour').delay(15000).fadeIn(1500).delay(3500).fadeOut(1500);
$('#picFive').delay(20000).fadeIn(1500).delay(3500);
});
</script>
and here is where it is implemented in the body code
<div id="pics">
<center>
<img src="img/dolllay.jpg" width="500" height="332" id="picFive" />
<img src="img/dye.jpg" width="500" height="332" id="picTwo" />
<img src="img/dollsit.jpg" width="500" height="332" id="picThree" />
<img src="img/heirloom.jpg" width="500" height="332" id="picFour" />
<img src="img/heritage.jpg" width="500" height="332" id="picOne" />
</center>
</div>
Could I turn it into a function and then loop it? Can I get any guidance on that? Thank you very much
Everyone's answering the question, but not solving the problem.
Sure, you can just put a loop wrapper around it (preferably one that doesn't terminate), but why not just program it right? Why have all the hardcoded times, and why not make it more robust?
Try rewriting your code like this. It makes it much easier to modify the pictures you loop through:
var pictures = ["picOne", "picTwo", "picThree", "picFour", "picFive"];
var index = 0;
var displayImage = function() {
if (index == pictures.length) { return; }
$("#" + pictures[index++]).fadeIn(1500).delay(3500).fadeOut(1500, displayImage);
};
displayImage();
Then, if you want to loop back, you simply tweak the displayImage function:
var displayImage = function() {
if (index == pictures.length) { index = 0; }
$("#" + pictures[index++]).fadeIn(1500).delay(3500).fadeOut(1500, displayImage);
};
TRY IT at jsfiddle
EDIT
On more careful reading of your question, I see that my original answer didn't do exactly what you needed. You have it set so that every five seconds, one will have faded out and the other one will have faded in. Currently, mine takes 6.5 seconds, since mine is all operating sequentially instead of concurrently. To make it come close to matching yours, just change the 1500s to 750s:
$("#" + pictures[index++]).fadeIn(750).delay(3500).fadeOut(750, displayImage);
This will take the right amount of time. It's slightly different from yours, in that one fades out all the way before the other fades in. The alternative is to actually skip the fadeIn and keep the fadeout. This is a lot closer to the way yours looks.
$("#" + pictures[index++]).show().delay(3500).fadeOut(1500, displayImage);
Or, make a very small fadein, to help reduce the flash of the new image:
$("#" + pictures[index++]).fadeIn(100).delay(3500).fadeOut(1400, displayImage);
Final Edit (really!)
Ok, to get the fadeIn and fadeOut to work reliably at the same time, the solution was to use neither. I went back to using animate, instead. As a result, I had to completely rewrite the displayImage function, but this is exactly what you need:
var displayImage = function () {
if (index == pictures.length) {
index = 0;
}
$("#" + pictures[index]).show().delay(3500).animate({
opacity: 0.2
}, {
step: function (now) {
var idx = (index + 1) % pictures.length;
var val = 1.2 - now;
$("#" + pictures[idx]).show().css("opacity", val);
},
complete: function () {
$("#" + pictures[index++]).hide();
displayImage();
}
});
};
What this does is move the sequence to "show->fadeIn and Out" instead of "fade in -> show -> fade out". To make your transition smooth, I only fade it out to 0.2 instead of 0. The step function is what fades the other one in at the same time. Once the new pic is visible, I completely hide the old pic.
Here's the working fiddle for it.
$(document).ready(function() {
setInterval(example, 10000); // repeat every 10 seconds
});
function example() {
$('#picOne').fadeIn(1500).delay(3500).fadeOut(1500);
$('#picTwo').delay(5000).fadeIn(1500).delay(3500).fadeOut(1500);
$('#picThree').delay(10000).fadeIn(1500).delay(3500).fadeOut(1500);
$('#picFour').delay(15000).fadeIn(1500).delay(3500).fadeOut(1500);
$('#picFive').delay(20000).fadeIn(1500).delay(3500);
}
A better way would be to give each pic the same class such as 'fadeinout'. This will mean you don't have to re-write your code when you add/remove more pics.
eg
<img id="picFive" class="fadeinout" ....
/* not sure if they are even <img>s but whatever they are*/
Then do
$(document).ready(function() {
beginFades();
});
function beginFades() {
$('.fadeinout').each( function(i,el) { // find all elements with fadeinout
//for each one, trigger the start of the fading after i*5000 milliseconds
//i is the index of the element as it was found by jQuery - this will be in
//document order (which actually may not be what you have but I'm guessing
//it is)
setTimeout(function(){
makeImgFadeInOut($(el))
}, i*5000);
});
}
function makeImgFadeInOut(el) {
//trigger a single fadeIn, fadeOut.
//But add a callback function to the end of fadeOut which retriggers the whole
//thing
el.fadeIn(1500).delay(3500).fadeOut(1500, function(){makeImgFadeInOut(el);});
}
WORKING DEMO (WITH DIVS)
You can use setInterval to loop it forever, or setTimeout to loop it for a specific duration.
<script type="text/javascript">
$(document).ready(function() {
setInterval(ImageSlider, 1000);
});
function ImageSlider() {
$('#picOne').fadeIn(1500).delay(3500).fadeOut(1500);
$('#picTwo').delay(5000).fadeIn(1500).delay(3500).fadeOut(1500);
$('#picThree').delay(10000).fadeIn(1500).delay(3500).fadeOut(1500);
$('#picFour').delay(15000).fadeIn(1500).delay(3500).fadeOut(1500);
$('#picFive').delay(20000).fadeIn(1500).delay(3500);
}
</script>
If you want to have total control upon your elements you can use this:
var elements = [{
el: '#pic1',
delay: 3500,
fadeIn: 1500,
fadeOut: 1500
},
{
el: '#pic2',
delay: 3500,
fadeIn: 1500,
fadeOut: 1500
}
//... other elements
]
var index = null;
(function loop(){
index = index || 0;
index = index % elements.length();
$(elements[index].el).fadeIn(elements[index].fadeIn, function(){
$(this).delay(elements[index].delay)
.fadeOut(elements[index].fadeOut, function(){
index++;
window.setTimeout(loop, 5000);
});
})();
Edit : forgot to execute the first iteration of the loop function and removing the useless call for index inside the loop
The good thing about how this loop works is that it doesn't use the SetInterval function.
and the code inside the loop need to finish what it does inside before iterating again.
(you won't have this hideous bug if you click an other tab and go back to your carousel)
#ElRoconno answer is pretty good too if you require less configuration
Use any of this-
setInterval() - executes a function, over and over again, at specified time intervals
setInterval(function(){alert("Hello")},3000);
setTimeout() - executes a function, once, after waiting a specified number of milliseconds.
setTimeout(function(){alert("Hello")},3000);
What is the difference between both setInterval and setTimeout
for you may be the setTimeout will not work as it will run only once after a delay and setInterval will go on to make continuous repetitive call until the window.clearInterval(intervalVariable) is been called
I have created an example on jsfiddler here. Basically you don't have to do this one at a time. Just get the whole collection of images as an array and loop over them. Hope this helps
$(document).ready(function () {
var arr = $('.pics')
arr.hide();
$(arr[0]).fadeIn(1500).delay(3500).fadeOut(1500);
var index = 1;
var maxIndex = arr.length - 1;
setInterval(function () {
/*arr.hide();
var pic = $(arr[index]);
pic.show();
*/
var pic = $(arr[index]);
pic.fadeIn(1500).delay(3500).fadeOut(1500);
index++;
if (index >= maxIndex) {
index = 0;
}
}, 6500);
});
There's really no need for setInterval here since you can use the callback built-into .fadeOut(), nor having to enumerate an array of images. You can do something as simple as:
var idx = 0;
fade();
function fade() {
if (idx >= $('img').length) idx = 0;
$('img').eq(idx).fadeIn(1500).delay(3500).fadeOut(1500, fade);
idx++;
}
jsFiddle example
Basically I need the thumbnails to rotate every time the user hovers over an image. Here is my failed attempt:
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.1/jquery.min.js"></script>
<script type="text/javascript">
$(function() {
$('img').hover(function() {
theImage = $(this).attr('id');
otherImages = $(this).attr('class').split('#');
rotateThumbs(otherImages, theImage);
}, function() {
//
});
});
function rotateThumbs(otherImages, theImage) {
for (i=0; i < otherImages.length; i++) {
setInterval($('#'+theImage).attr('src', otherImages[i]), 1000);
}
}
</script>
<img id="myImage" src="http://www.google.com/images/logos/ps_logo2.png" class="http://www.google.com/images/logos/ps_logo2.png#http://l.yimg.com/a/i/ww/met/yahoo_logo_us_061509.png#http://dogandcat.com/images/cat2.jpg" width="174" height="130" />
Does anyone know how this may be accomplished?
Some issues here.
setInterval requires a function reference as it's first argument, but you are executing code that returns a jQuery object.
setInterval executes the first function repeatedly at the specified interval. Is that what you are trying to do? Swap images every second?
Depending on how you correct the first issue, you could run into an issue where i is otherImages.length and thus the src is set to undefined.
Assuming you worked around issue 3, you will have the problem that the image swaps will happen imperceptibly fast and it will appear as though the last image is always displayed.
Instead, don't use a loop. Increment a counter each time a new image is displayed. Try this:
function rotateThumbs(otherImages, theImage) {
var i = 0;
var interval = setInterval(function() {
$('#'+theImage).attr('src', otherImages[i++]);
if (i >= otherImages.length) {
clearInterval(interval);
}
}, 1000);
}
I've implemented a fully-functional example here. This addresses some of the issues that #gilly3 notes, but uses closures instead of an incrementing counter to keep track of the current image:
$(function() {
$('img').hover(function() {
// declaring these variables here will preserve
// the references in the function called by setInterval
var $img = $(this),
imageList = $img.attr('class').split('#'),
intervalId;
// start the cycle
intervalId = window.setInterval(function() {
var next = imageList.pop();
if (next) {
$img.attr('src', next);
} else {
// stop the cycle
intervalId = window.clearInterval(intervalId);
}
}, 1000);
}, function() {});
});
As you can see, using a closure is much easier when you declare the function passed to setInterval inline, rather than as a separate, named function. You could still have a rotateThumbs function if you wanted, but you might need to do some more work to ensure that the variables were being passed properly.
Edit: I made an updated version that continues to cycle as long as the mouse is hovering.
I have adjusted the answer for Sam, taking pre-loading the image into account, so that you won't have a possible deplay at the first rotation.
function rotateThumbs(otherImages, theImage) {
if(!$('#'+theImage).data('setup')){
$('#'+theImage).data('setup', true); // do not double pre-loading images
var $body = $('body');
for(var j = 0; j < otherImages.length; j++){
$body.append($('<img/>').attr('src', otherImages[j])
.css('display', 'none'));
}
}
var i= 0;
setInterval(function(){
$('#'+theImage).attr('src', otherImages[i++]);
if(i >= otherImages.length){i = 0}
}, 1000);
}
I am aware that when coding an extension, there is no way we can delay a function call except for using a setTimeout call but here's what I am trying to achieve in a plugin that I am developing for Firefox (this is not for Javascript embedded into a web page by the way):
for (var i = 0; i < t.length ; i++) {
//Load a URL from an array
//On document complete, get some data
}
The idea is simple. I have an array of URLs that I want to parse and extract some data out of. Each of these URLs take some time to load. So, if I try to get some data from the current page without waiting for the page to load, I will get an error. Now, the only way to do this as I know is as follows:
firstfunction: function() {
//Load the first url
setTimeout("secondfunction", 5000);
}
secondfunction: function() {
//Load the second url
setTimeout("thirdfunction", 5000);
}
And so on... I know this is obviously wrong.. I was just wondering how people achieve this in Javascript...
EDIT: Sorry about not being more detailed...
I'm not convinced that this type of foolery is necessary but I'm not an extension dev so who knows. If this is the approach you want, then just have the setTimeout call refer to the same function:
var index;
firstfunction: function() {
// do something with `index` and increment it when you're done
// check again in a few seconds (`index` is persisted between calls to this)
setTimeout("firstfunction", 5000);
}
I am not sure how to do this from a plugin, but what I've done with iframes in the past is attach a callback to the target document's onLoad event.
Maybe something like:
var index = 0;
var urls = [ ..... ];
function ProcessDocument() { ....; LoadNextDocument(); }
function LoadNextDocument() { index++; /* Load urls[index] */; }
document.body.onLoad = ProcessDocument;
Somewhere in there you'd need to test for index > urls.length too for your end condition.
I had same problem but I used recursion instead of looping.
Below is the running code which changes the innerHTML of an element by looping through the list. Hope its helpful.
<Script type="text/javascript">
var l;
var a;
function call2()
{
l = document.getElementById('listhere').innerHTML;
a = l.split(",");
call1(0);
}
function call1(counter)
{
if(a.length > counter)
{
document.getElementById('here').innerHTML = a[counter];
counter++;
setTimeout("call1("+counter+")",2000);
}
}
</Script>
<body onload="call2()">
<span id="listhere">3,5,2,8</span><Br />
<span id="here">here</span>