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How to have JavaScript functions work across different HTML pages?

I am building a website with several HTML pages, and going to fill up info on different pages through an API. I have added onclick listeners to HTML elements like this:
// ASSIGNING ELEMENTS AS VARIABLES
const EPL = document.getElementById('epl');
const bundesliga = document.getElementById('bundesliga');
const laliga = document.getElementById('laliga');
// ONCLICKS
EPL.onclick = function() {
getStandings('2021');
location.replace('standings.html');
}
bundesliga.onclick = function() {
getStandings('2088');
location.replace('standings.html');
}
laliga.onclick = function() {
getStandings('2224');
location.replace('standings.html');
}
When one of these is clicked, I call a function (getStandings) with its unique argument to fetch some data from the API. I also want to move to another HTML page, for which I used location.replace.
I'm caught in a dilemma: if I use the same JS file for every HTML page, when I get to the new HTML page, I get errors as the new HTML page does not have every element:
main.js:41 Uncaught TypeError: Cannot set property 'onclick' of null
But if I use different JS files, maybe one JS file for each HTML file, I cannot carry forward the bits of information I need. How can I get to the new HTML page, with its own JS file, without stopping and losing everything in the function I'm in currently, under the JS file of the old page? For example, the argument '2021' or '2088' are to be passed into the getStandings() function which will populate the new HTML page with data from an API. If I jump to a new HTML page with a new JS file, this is lost.
Is there a better way to organise my files? 😐😐😐😐😐

You can set your event listeners on the condition that the elements are not null e.g.
const EPL = document.getElementById('epl');
const bundesliga = document.getElementById('bundesliga');
const laliga = document.getElementById('laliga');
if(EPL){
EPL.onclick = function() {
getStandings('2021');
location.replace('standings.html');
}
}
etc...

Solved! As amn said, I can add URL parameters to the end of the URL of the new HTML page, then get the variables from its own URL once I'm on the new HTML page.

I think I would rather use classes instead of IDs to define the listener, and maybe IDs for dedicated action.

Liferay 7: Using URL params and Javascript to prefill a form

I've been working with Liferay 7 for a while and needed to create a feedback form with prefilled values. I created a feedback form and a page, where it's shown and where I could add Javascript.
The user clicks on a link ("Did you find this helpful? Yes/No") and it takes you to the feedback page with the page and answer as URL parameters.
URL: {feedback-page-url/} ?pageUrl=/services&answer=Yes
Now here's where the problems began. Liferay updates it's values very confusingly and while generic document.getElementsByName(...) etc. seemed to work at first, they updated back when clicking the page. The difficult thing is to update the right values in right elements, so they won't be overrun by Liferay.
I provided an answer to my question below. Feel free to ask me anything, I'll try to help :)

Full code block in the end!
So I found out a solution to this problem. Liferay creates an instance (_com_liferay...) and uses it's values to be up to date, so we need to get a hold of it and update it's values. You can do it manually by inspecting and finding your instance, but I have an automatic code that should get it for you.
The id we are searching for is for DDMFormPortlet and the String we get this way is close to perfect. The String that document.querySelector() finds begins with p_p_id_com..., so we can use .substring to remove the unnecessary part and then add +"form" in the end to make it complete. If you find a better way to find this, please share it :)
// _com_liferay_dynamic_data_mapping_form_web_portlet_DDMFormPortlet_INSTANCE_randomkey_form
const idFinder = function() {
const idString = document.querySelector('[id*="DDMFormPortlet"]').id;
return(idString.substring(6) + "form");
}
Now that we have the correct String text, we'll find the element, that corresponds to it:
const formFieldArray = window[idFinder()];
Now if you try it just by itself, it most likely won't find anything, because it's loads slowly. I put all of this into try-catch with setTimeout() to make sure everything works as intended. Now all we need to do is collect the information from our URL and set it to the correct places.
const params = new URLSearchParams(location.search);
const formAutoFiller = function (params) {
try {
const formFieldArray = window[idFinder()];
// make sure you have the numbers according to your form!
formFieldArray.pages[0].rows[0].columns[0].fields[0].value=params.get('pageUrl');
formFieldArray.pages[0].rows[1].columns[0].fields[0].value=params.get('answer');
// ...
}
}
And finally, as the changed values update to the form after clicking an input field, we'll move the selection focus to one of the input fields after the other code is ran:
document.getElementsByClassName("ddm-field-text")[1].focus();
A bit cleanup for myself and we're done! Full Javascript here:
const params = new URLSearchParams(location.search);
const idFinder = function() {
const idString = document.querySelector('[id*="DDMFormPortlet"]').id;
return(idString.substring(6) + "form");
}
const formAutoFiller = function (params) {
try {
const formFieldRows = window[idFinder()].pages[0].rows;
formFieldRows[0].columns[0].fields[0].value=params.get('pageUrl');
formFieldRows[1].columns[0].fields[0].value=params.get('answer');
document.getElementsByClassName("ddm-field-text")[1].focus();
} catch (e) {
setTimeout(formAutoFiller, 500, params);
}
}
formAutoFiller(params);

Change thousands sign using JS

Here I would like to replace in the draggable slider the "," sign used for the thousands into this sign " ' " (a quote mark).
I am currently using a plugin to render the table (from a JSON file) so I cannot alter the HTML.
I am able to change the sign, in fact on page load the sign seems correct, but as soon I drag the slider the separator changes to a comma again.
I saw that the data is rendered from the Plugin with a comma in the aria-valuetext="" attribute: <div class="noUi-handle noUi-handle-upper" data-handle="1" tabindex="0" role="slider" aria-orientation="horizontal" aria-valuemin="0.0" aria-valuemax="100.0" aria-valuenow="100.0" aria-valuetext="2,290.00"><div class="noUi-tooltip">2,290.00</div></div>
I tried using this code without any results:
<script>
window.onload = function(){
var div = document.querySelectorAll('.noUi-tooltip');
div.forEach(function(r) {
var text = r.textContent;
var output = text.replace(/[,|]/g, "'");
r.innerHTML = output;
});
}
</script>
What am I writing wrong?
I am using WordPress and the wpdatatables plugin.

I'm not sure about the plugin you've used for your slider but perhaps you can try this for now:
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(mutation) {
if (mutation.type == "attributes") {
var parentEl = document.getElementsByClassName('noUi-handle-upper');
var childEl = parentEl.childNodes[0];
childEl.innerHTML = childEl.innerHTML.replace(',', '\'');
}
});
});
observer.observe(document.getElementsByClassName('noUi-handle-upper')[0], {
attributes: true,
});
It's using MutationObserver which is not supported by older browsers. You can read more about it at https://developer.mozilla.org/en-US/docs/Web/API/MutationObserver.

This is because you modify the string just in the beginning (on load).
This is why the code works in the beginning but doesn't work later, because it runs once and then stops.
I don't know how to use WordPress or sliders, but I'd advise you to use an 'on value changed' command, so the text will change to whatever you want it to each time the slider's value is changed.
I will post this now but I'll review your code and will try to update this with more exact information later.

Including a javascript function in a custom joomla module

I have a working codepen that uses some javascript
https://codepen.io/cbold/pen/jOWONKO
I am struggling to understand the correct method/syntax for including the javascript function with my custom Joomla module.
I have read the official documentation but it does not make it any clearer for me
https://docs.joomla.org/J3.x:Adding_JavaScript_and_CSS_to_the_page
I have also looked at several other similar questions posted on Stackoverflow, but I do not understand any of the examples/answers enough to apply them to my module.
I have tried to include the function as a separate file, and invoke it with my mod_mymodule.php :
$document = JFactory::getDocument();
$document->addScript(JURI::root(true)."modules/mod_mymodule/js/ mod_mymodule.js");
This is the javascript in mod_mymodule.js:
function clickHandler(target) {
// Get the element that should be selected
const elem = document.querySelector(target);
// There were no elements to be selected
if (!elem) return;
// Get the old selected element (if any)
const prevElem = document.querySelector('.selected');
if (prevElem) {
// If there was a previously selected element, it isn't anymore
prevElem.classList.remove('selected');
}
// Make the new element selected
elem.classList.add('selected');
}
The function does not occur.
I have tried both document.querySelector(target); and document.querySelector('#target');
I have also tried including the function at the end of my module’s default.php
<script type="application/javascript">
function clickHandler(target) {
// Get the element that should be selected
const elem = document.querySelector(target);
// There were no elements to be selected
if (!elem) return;
// Get the old selected element (if any)
const prevElem = document.querySelector('.selected');
if (prevElem) {
// If there was a previously selected element, it isn't anymore
prevElem.classList.remove('selected');
}
// Make the new element selected
elem.classList.add('selected');
}
</script>
But no luck.
Again I have tried both document.querySelector(target); and document.querySelector('#target');
I am pretty certain my <script> is wrong, but I don’t know enough about javascript – specifically the proper syntax required by Joomla – in order to make it work directly from my module.php.
Any help is greatly appreciated.

This ended up working for my needs, a short script in the module's default.php
<script>
jQuery('.target').click(function(){
var id = jQuery(this).attr('id');
jQuery('body').find('.selected').removeClass('selected');
jQuery('#target'+id).addClass('selected');
});
</script>

iBooks Author/iAd Producer Widget User Text Disappears

I'm using iAd producer to create HTML widgets for iBooks I'm making using iBooks Author. I've done some research and learned that I can have user input saved into local storage by way of a variable that is called every time the widget is opened. This is great except for the new problem of having to create hundreds of text box widgets all with different variables so I can use these text boxes on multiple pages. Is there a way for me to automate this using Java Script? One idea I had was to use a "while" function to tell the script to ++ the variable if the one it tried to use was not empty. Example: the variable "001" was already used so the code would ideally set the next user text to variable "002". Preferably, I'd like to be able to create one widget with this code that I could reuse anywhere else.
Here is the code I'm currently using:
/*Widget code*/
this.onViewControllerViewWillAppear = function (event) {
var theValue = this.outlets.textField;
if (localStorage.getItem("theKey102") === null) {
theValue.value = "";
} else {
theValue.value = localStorage.getItem("theKey102");
}
};
/*This is the code for one of the text boxes I'm using */
this.onControlValueChange = function (event) {
var theValue = this.viewController.outlets.textField;
localStorage.setItem("theKey102", theValue.value);
};