Develop Reference

JavaScript works when setTimeout() is used, but it isn't working when document.eventListener('DOMContentLoaded', x) is used on a WordPress page. Why?

I have a few lines of JavaScript code that pick up heading texts from separate sections and place them into their respective input fields. They are also executed on single pages using wp_enqueue_script.
It works absolutely fine when setTimeout() is used:
function passengerElevator() {
var getProductName = document.querySelectorAll('[data-id="6657316"]');
getProductName.forEach(function(item) {
var productName = item.querySelector('.lift');
var inputArea = item.querySelector('input[name=product]');
inputArea.value = productName.innerText;
});
var getProductName = document.querySelectorAll('[data-id="e9c06d5"]');
getProductName.forEach(function(item) {
var productName = item.querySelector('.lift');
var inputArea = item.querySelector('input[name=product]');
inputArea.value = productName.innerText;
});
setTimeout(function() { passengerElevator() },3000);
However, there is problem of page size (some pages have more than 10 input fields) and I don't want to set an astronomically high ms to delay the script. So I decided to fire it on DOMContentLoaded:
document.addEventListener("DOMContentLoaded", passengerElevator);
function passengerElevator() {
var getProductName = document.querySelectorAll('[data-id="6657316"]');
getProductName.forEach(function(item) {
var productName = item.querySelector('.lift'); // heading text (ex:Panoramic Lift)
var inputArea = item.querySelector('input[name=product]');
inputArea.value = productName.innerText; //ouput here
});
var getProductName = document.querySelectorAll('[data-id="e9c06d5"]');
getProductName.forEach(function(item) {
var productName = item.querySelector('.lift'); // Heading text (ex:Home Lift)
var inputArea = item.querySelector('input[name=product]');
inputArea.value = productName.innerText; // Output here
});
}
As you may have already guessed, it is not working. Is my code too messy to be executed faster or is there any other problem I am missing?
I know similar questions have been asked previously, however, no existing answer I found was able to help me.

It seems like you try to loop through elements that are still not loaded. Perhaps they are being appended to the page via Ajax, so DOMContentLoaded can't help there.
You can create your own check for those elements using setInterval, so use something like this:
let dataIdCheck = setInterval(() => {
if (document.querySelectorAll('[data-id="6657316"]').length > 0 && document.querySelectorAll('[data-id="e9c06d5"]').length > 0) {
clearInterval(dataIdCheck);
// your code here
}
}, 500);
This code will run every 500 milliseconds and check if those two elements exists, using .length. Once they do exists, we stop the interval and run the code.
I also suggest to do console.log('in') to check that our interval stop running once the elements are found.

jQuery prevent reload if button clicked

I have a jQuery datatable that immediately loads ON READY. After that, the datatable is reloaded every 30 seconds. This feature is functioning properly.
I have added a search feature that automatically reloads the datatable with new search results. This part is also functioning properly.
The problem I am experiencing is when I am using the search feature, and the new search results are returned. After 30 seconds, the new results are cleared and the datatable reloads with all of the original records.
Here is what I am currently attempting:
$(document).ready(function()
{
var searchCriteria = "";
displayBookings(searchCriteria);
var idle = 0;
var idleInterval = setInterval(timer, 30000);
$(this).mousemove(function(e){idle = 0;});
$(this).keypress(function(e){idle = 0;});
function timer()
{
idle = idle + 1;
if(idle > 2)
{
displayBookings(searchCriteria);
console.log('table reloaded');
}
}
$('#searchPending').on('click', function()
{
var isPending = 'Y';
var searchCriteria = {
isPending: isPending
};
displayBookings(searchCriteria);
});
});
The function displayBookings() takes searchCriteria. If searchCriteria is blank, then a basic query is fired. Obviously is searchCriteria contains parameters, then the same query is fired with a WHERE clause attached. I did not disclose the code for displayBookings().
All I need to do is stop the 30 second interval if the #searchPending button is clicked.

Clear the interval so it will stop loading.
clearInterval(idleInterval)
specifically in your code:
$('#searchPending').on('click', function()
{
clearInterval(idleInterval)
var isPending = 'Y';
var searchCriteria = {
isPending: isPending
};
displayBookings(searchCriteria);
});

Rather than start and stop the timer interval, since you'll run into a bit of a race condition, you can just have the "refresh" (your "timer" function) refresh using the latest search criteria. To do this, just pass the same object into your displayBookings function. E.g.
const search = { criteria: "" };
$(...).click(() => {
search.criteria = 'change it...';
displayBookings(search.criteria);
});
setInterval(() => displayBookings(search.criteria), 30000);
This way, if a refresh happens, it will use the latest search.criteria. You can achieve the same result with minimal change in your code by simply removing the var from the second searchCriteria. Currently, without removing the var, your outer criteria is being "shadowed" by your inner.
I alluded to debouncing1 in one of my comments. I misread the code and debouncing is not what you want. Instead, you want to only "refresh" if there hasn't been any user activity within some threshold. Here's an alternative from the approach you used:
let lastInteraction = 0;
function interact() {
lastInteraction = Date.now();
}
$(this).mousemove(interact);
$(this).keypress(interact);
Then in your refresh function:
if (Date.now() - lastInteraction > threshold) { ...
Implementing both the central criteria and revised idle check:
$(document).ready(function() {
const idle = {
threshold: 1000,
lastInteraction: 0,
interact() {
idle.lastInteraction = Date.now();
},
isIdle() {
return Date.now() - idle.lastInteraction > idle.threshold;
}
};
const search = { criteria: "" };
$(this).mousemove(idle.interact);
$(this).keypress(idle.interact);
setInterval(() => {
if (idle.isIdle()) {
displayBookings(search.criteria);
}
}, 30000);
$('#searchPending').on('click', () => {
search.criteria = { isPending: 'Y' };
displayBookings(search.criteria);
});
displayBookings(search.criteria);
});
1 The Wikipedia article linked to discusses debouncing with a keyboard. It's the same concept. You'd use debouncing on your displayBookings function if you plan on having it execute live as the user is typing. This would prevent too many HTTP requests from happening in a short duration of time.

function increment sync with video (or auto increment)

I'm busy with a webdoc that I'm partially creating on hype, the video are hosted on vimeo (so I need to use the vimeo api for some tasks like seekto) but my difficulties should be limited to js.
the objective is to display a given image at a given time interval of the video.
With my code below, I do get the string "test", "success" and "confirmed success" at the right time in my div id=popimgbox, and I can seek back and forth in the video and still get the right "answear", if I may say so.
Now, I have images that are all stored in the same folder, and all named popimgX.jpg, with X being a number.
I want
to store the URLs of my images in a variable let's say "popimgurl"
that my variable is updated (by a function???) in order to contain the URL of a given immage for a given interval of time of the video
to still be able seekto back and forth in the video and get the right URL at the right time
To do so I created a function increment, and a pair of variable. With the code below, my popimgurl variable is indeed updated once the video reach 3 seconds, but it do not increment only once... untill the video reach 6 seconds, when I want to update my popimgurl variable once again.
I tried to use for with js break and js closure but did not manage for some understandable reasons after thought;
I did quite some try with switch, but I'm stuck with the fact that the case must be string or single numerical value, not numerical interval or comparaison.
thank's in advance for your help :-)
var iframe = $('#vplayer_1')[0];
var player = $f(iframe);
var status = $('.status');
fired = 0;
//my try to sync increment
var dia = (function () {
var n = 0;
return function increment() {return n += 1;}
})();
function dian(){
popimgurl = '${resourcesFolderName}/popimg'+ dia() +'.jpg';
popimgloader = '<img src ="' + popimgurl + '">';
}
// When the player is ready, add listeners for pause, finish, and playProgress
player.addEvent('ready', function() {
status.text('ready');
player.addEvent('pause', onPause);
player.addEvent('finish', onFinish);
player.addEvent('playProgress', onPlayProgress);
});
// Call the API when a button is pressed
$('button').bind('click', function() {
player.api($(this).text().toLowerCase());
});
function onPause(id) {
status.text('paused');
}
function onFinish(id) {
status.text('finished');
}
function onPlayProgress(data, id) {
status.text(data.seconds + 's played');
//my chapters, when I want the img to change within popimgbox
if (data.seconds >= 1) {
popimgbox.innerHTML = "test";
}
if (data.seconds >= 3) {
// popimgbox.style.display = "success"
dian();
popimgbox.innerHTML = popimgurl;
}
if (data.seconds >= 6) {
// popimgbox.style.display = "confirmed success"
dian();
popimgbox.innerHTML = popimgurl;
}
}
PS1: disclamer, I'm a beginer coder, i do my best so excuse my french if my question isn't well formulated or if the answer is somewhere but I was unable to see/understand it
PS2 : i did quite a try with popcornjs, but not way to make it work with vimeoapi and within hype, quite frustrated ;-)
PS3: as this is my first post I would like to thank's you all for the great support available here; I owe you most ;-)

Finally I'll answer myself.
It's a solution that only stand for vimeo, as this is what I use to host my videos, but very little changes have to be done to work with the html5 <video> tag as well.
First you need to define your variables and your intervals:
var intervals =[11.56, 44.08, 115, 125, 127.92, 177.72];
var index;
Then you need to add an event listener timeupdate that return the elapsed time , filter intrevals according to the elapsed time data.seconds or seconds and define the value of index as the indexOf the last entry of your filtered array intervals
player.on('timeupdate', function(data) {
seconds = data.seconds;
index = intervals.indexOf(intervals.filter(function(nb) {
return seconds < nb;
})[0]);
if (diaIndex == -1) {
// do something if seconds > the higher value of your last interval
}
And that's it !
Now for
seconds = [0, 11.56[ --> index = 0
seconds = [11.56, 44.08[ --> index = 1
seconds = [44.08, 115[ --> index = 2
and so on
Now we can use index as a variable for instance to display a given image :
var imgNum = 0;
function diaplayImg(index) {
if(index === imgNum) {
return;
// this will avoid that the same image is releaded on every timeupdate events
}
else {
imgNum =+ index
document.getElementById('myImageWraper').innerHTML = "<img src='img" + imgNum+ ".png'>"
};
}
Don't forget, you need to call the function displayImage() in your timeupdate event listener, it will then be fired every ±250ms but the image won't be reloaded each time
PS : vimeo has realeased its new api between my question and my answer so the question use the old api while the answer use the new one

how to bypass the setTimeout throttle in a hidden tab?

I'm am doing a heavy "scientific" (ie, not displaying data) webgl computation. Webgl can't be put in a worker, and doing a lot of webgl blocks the whole browser so I sliced my computation in chunks, and I compute each chunk in a setTimeout() function (after calling getError() to flush the opengl queue). I leave a bit of time in between the chunks so that the browser has time to flush some UI events from the main UI queue and it makes the whole thing feel a bit less sluggish.
My problem is that when the tab is hidden, the setTimeout gets throttled to a one second period which is way too slow for me.
Is there a better solution than what I did? Obviously requestAnimationFrame() doesn't work, since it's never called back in hidden tabs (and it's too slow in visible).
Is there a non-throttled time event in the hidden state? I tried to use window.postMessage() but it's still too fast and the whole browser feels slow.
here is the current state of my research:
function drawTile(sequenceIndex) {
if (sequenceIndex < sequence.length) {
var x = sequence[sequenceIndex][0];
var y = sequence[sequenceIndex][1];
setTilePos(x, y);
modelStage.render(renderer, modelBuffer);
minkowskiPass.render(renderer, minkowskiBuffer, modelBuffer);
copyPass.quad.position.x = x;
copyPass.quad.position.y = y;
copyPass.render(renderer, null, minkowskiBuffer);
var gl = renderer.getContext();
gl.getError();
sequenceIndex++;
if (document.visibilityState != "hidden") {
setTimeout(function () {
drawTile(sequenceIndex);
}, 10);
} else {
//window.postMessage is not rate limited then the tab is hidden
// we need to slow the computation by an event, otherwise the whole browser is unresponsive.
$(window).one('message', function () {
drawTile(sequenceIndex);
});
window.postMessage('lol', '*');
}
} else
console.timeEnd('computation');
}
console.time('computation');
drawTile(0);

Here's another convoluted workaround for anyone who needs it; you can use the Web Audio API to generate function calls:
var setTimeout2 = (function () {
var samples = 2048;
var fns = [];
var context = new AudioContext();
var source = context.createBufferSource();
var node = context.createScriptProcessor(samples, 1, 1);
// This gets fired every ~46 milliseconds. You can change
// `samples` to another valid value (256, 512, 1024, 2048,
// 4096, 8192, or 16384); then it'll get called every
// `samples / context.sampleRate` seconds (~46 ms for
// `samples == 2048` and `context.sampleRate == 44100`).
node.onaudioprocess = function (e) {
fns = fns.filter(function (fn) {
return !fn(Date.now() - fn.t);
});
};
source.connect(node);
node.connect(context.destination);
window.do_not_garbage_collect = [context, source, node];
return function (fn) {
fn.t = Date.now();
fns.push(fn);
};
}());
// Use like this:
setTimeout2(function (t) {
console.log(t);
// End after 1 second.
if (t > 1000)
return true;
})

Perhaps have a worker thread also run a
postMessage loop and a fraction of the time (every n iterations), either pause or resume the main thread?

Rate limiting to prevent malicious behavior in ExpressJS

Someone made me aware of some flaws in an application I'm working on (mostly within my JavaScript on the front-end), that leaves open the possibility of, say, clicking a ton of buttons at once and sending out a ton of transactional emails. This is clearly not good.
I think one way to handle this in ExpressJS is by using app.all() to count the number of requests that happen within a certain timeframe. I'd store this in the session metadata with timestamps, and if more than X requests happen in Y time, I cut them off for awhile until the limit expires.
Has anyone done this before or have any tips/hints to help me out? Something that's easy to drop in and out of my app is preferable. Thanks!

You could use the Collate object in your webpage.
function Collate(timeout) {
this.timeout = timeout || 1000;
}
Collate.prototype = {
time: 0,
idle: function() {
var t = new Date().getTime();
return (t - this.time > this.timeout && (this.time = t));
},
prefer: function(func) {
this.func = func;
clearTimeout(this.timer);
this.timer = setTimeout(func, this.timeout);
}
};
If you want a function to run once and not run again within the next 1 second.
Like if you want to prevent the user from submitting a form many times, you do this:
var timer = new Collate(3000); //3 seconds
button1.onclick = function() {
if(timer.idle()) {
button1.form.submit();
} else alert("Don't click too quickly!");
}
//or on the form tag
<script>var submitTimer = new Collate(3000);</script>
<form action="post" onsubmit="return submitTimer.idle();">
If you expect an event to fire multiple times and only want to react to the last time it fires.
Like if you want to search after a user has finished typing, you do this:
var timer = new Collate(700); //0.7 seconds
textfield1.onkeyup = function() {
timer.prefer(function() {
autocomplete.search(textfield1.value);
});
};