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Clear dropdown Select2 populated from JSP / Ajax with a button only works once

I have a page in which to make a query to the database, 12 filters are applied (each filter corresponds to a select2 dropdown).
When the page loads, the selects are filled by default with data from the java controller.
Example from a jsp page:
<select id="selectFPA" name="selectFPA" form="formResult" class="form-control">
<option selected>All the results</option>
<c:forEach items="${fpaList}" var="fpaList">
<option><c:out value="${fpaList.fpaname}" /></option>
</c:forEach>
</select>
But, if the user selects any value in any of the filters, all the filters are updated based on the chosen selection, through an AJAX call.
For example, suppose we have two select filters (dropdown):
Select 1 (Animal group):
- Birds
- Mammals
Select 2 (Animal name):
- Parrot
- Dog
If the user chooses mammals, an AJAX function will be called that will query the database and update the content of the select 2, eliminating the Parrot option. (And so on with up to 12 filters).
The problem comes when I want to clear the applied filters and return to the original select content (the content that appears by default every time the page is loaded from the java controller).
I have tried many things, from similar Stackoverflow questions without success.
The last thing I tried was:
Save the initial content of the select in a variable:
const fpa = $("#selectFPA").find("option").clone();
Onclick event (Reset filters button)
$("#ResetFilters").on("click",function() {
//first we empty the content
$('#selectFPA').empty().trigger('change.select2');
//original value injection
$("#selectFPA").html(fpa),
$('#selectFPA').trigger('change.select2')
})
This works fine if I press the button once, if I press the button a second time, the selects randomly select different values by default and they behave strangely.
I know this is a very specific question, but could someone help me? What am I doing wrong?
Thank you.

I think as per this answer you cannot create constant in jquery that's the reason only first time it works and next time it doesn't .Alternate, solution might be assign that clone value to some div and fetch it anytime when needed.Like below :
//call when page loads for the first time
$(document).ready(function() {
//cloning
var fpa = $("#selectFPA").find("option").clone();
//assigning value to div
$("#abc").html(fpa);
$("#ResetFilters").on("click", function() {
//getting clone value from div
var c = $("#abc").find("option").clone();
//first we empty the content
// $('#selectFPA').empty().trigger('change.select2');
//original value injection
$("#selectFPA").html(c);
//$('#selectFPA').trigger('change.select2')
});
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<select id="selectFPA" name="selectFPA" form="formResult" class="form-control">
<option selected>All the results</option>
<option>1</option>
<option>2</option>
</select>
<button id="ResetFilters">Reset</button>
<div id="abc" style="display:none"></div>

How to prevent Angular1.0 select (dropdown) extra white space?

I am working on an AngularJS 1.0 application and facing an issue with Angular Select.
Just Copying a dummy code:
<select ng-model ="data.state" ng-options="data.states">
Select
Here, it's listing states of a country and passing a default data as ng-model.
I need to show a text "Select" if default is not matching with the data source.
But it's not working as expected and it's showing an extra empty space instead of select.
Thanks

"I need to show a text "Select" if default is not matching with the data source." In this case your data.state may be empty (ie "") case. You may be expecting some logic like this:
<label>States : </label>
<select ng-model ="data.state" ng-options="data for data in data.states" >
<option value="" selected hidden >SELECT</option>
<!--Removes the Empty space and shows "SELECT" as pre-populated by default in the drop-down. -->
</select>
<br>Selected State : {{data.state}}
Empty space appears as a placeholder offered by Angular to hold text like "Select an option" or "Choose a best answer". You can override this using the <option value="" selected hidden >Select</option> which won't appear in the selected drop down options list as it is hidden.
If you wish to have the select appear as an option for user to choose in order if the field can be remained empty and is not mandatory you can use the following code instead:
<option value="" selected >SELECT</option>
In controller expecting the data as:
// $scope.data.state = something that is returned from some API response
$scope.data = {
states: [
"Kerala",
"Karnataka",
"Andhra",
"Haryana"
]
}
Checkout the JS Fiddle here for working sample.

<select ng-model ="data.state" ng-options="data.states">
make use of track by in ng-repeat. track by $index or id if any

Combining javascript and jquery to fill multiple hidden fields - bad idea?

I'm trying to find the best way to make my teachers' lives a little easier.
I've got a select field and list of options generated by a tlist sql query. The select field itself already has a javascript attached to it, which fleshes out other field values (credit values and credit types) elsewhere based on the id of the select option chosen. This is the javascript that works for that purpose:
<script type="text/javascript">
function changeValue(){
var option=document.getElementById('courseno').value;
if(option=="E100"){
document.getElementById('credval').value="10";
document.getElementById('credtype').value="EngFresh";
}
else if(option=="E200"){
document.getElementById('credval').value="10";
document.getElementById('credtype').value="EngSoph";
}
}
</script>
I also need to populate a hidden field that is (and must remain) outside the tlist sql tag that generates the select list.
Here is my sql code:
<select id="courseno" name="course_number" onchange="changeValue();">
<option value="">Select a Course</option>
~[tlist_sql;
SELECT cc.course_number, cc.section_number, c.COURSE_NAME
FROM cc cc
RIGHT JOIN COURSES c ON c.COURSE_NUMBER = cc.course_number
RIGHT JOIN STUDENTS s ON cc.studentid = s.id
WHERE cc.studentid = ~(curstudid)
AND TERMID = ~(curtermid)
AND c.CreditType LIKE 'English%'
AND NOT EXISTS (
SELECT * FROM storedgrades sg
WHERE sg.studentid = ~(curstudid)
AND sg.course_number = c.course_number
)
ORDER BY c.course_name;]
<option name="~(course_no)" value="~(course_no)" id="~(secno)">~(course_no).~(secno) (~(cname))</option>
[/tlist_sql]
</select></td>
</tr>
And just below that is the hidden field I would like to populate:
<td width="25%" class="bold"> </td>
<td><input type="text" id="secnum" name="section_number" value=""> </td>
I gave each of the options the section number as its ID, thinking I could use the ID element of each of those options and some clever jquery to populate the hidden field, but I'm having no luck. I just read on another question that was ably answered by the community that you shouldn't use an option ID tag that begins with a number... so now what can I do?
Could somebody please help me?
Thanks forever,
Schelly

I don't think your problem comes from the ID being a number. We haven't seen what jQuery you've tried, but you most likely don't need jQuery at all. Assuming what you have is working correctly, and the PowerSchool code is putting out elements the way you expect them to be (View Source in your browser to be sure, if this doesn't work), you should be able to grab the ID from the selected option inside your changeValue function, store it in a variable, and push that value into the "secnum" field as follows:
function changeValue(){
var courseDropdown = document.getElementById('courseno');
var selectedElement=courseDropdown.options[courseDropdown.selectedIndex];
var option=selectedElement.value;
var courseNo = selectedElement.getAttribute("id");
if(option=="E100"){
document.getElementById('credval').value="10";
document.getElementById('credtype').value="EngFresh";
}
else if(option=="E200"){
document.getElementById('credval').value="10";
document.getElementById('credtype').value="EngSoph";
}
document.getElementById('secnum').value=courseNo;
}
I changed the way that your "option" variable is being set, but it will work the same way. You might end up wanting to move the last line, where the "secnum" field is being set, or wrap it in an "if", etc.; I don't know your full requirements.
All that said, there would be nothing wrong with using jQuery in this situation, but it's not necessary in this case unless you need extreme backwards-browser compatibility.

Working Example Here
You can use multiple on change events to do whatever you want. On change add a new event and populate the hidden input. You can define custom attributes to any html element with any data that is required to populate the hidden input
<select id="myselect">
<option>Select</option>
<option data-number="1">One</option>
<option data-number="2">Two</option>
<option data-number="3">Three</option>
<option data-number="4">Four</option>
<option data-number="5">Five</option>
</select>
<input type="hidden" id="hiddenInput"/>
$(document).ready(function(){
$('#myselect').on('change', mySelectChange);
function mySelectChange(){
console.log('your standard change value here');
}
$('#myselect').on('change', mySelectChange2);
function mySelectChange2(){
var option = $("#myselect option:selected");
console.log(option.text());
console.log(option.attr('data-number'));
}});

Using select2.js with multiple select optgroup and knockoutJS

I am trying to achieve a databinding for multiple selection with optgroup using knockoutJS. In addition we would like to use select2 for its search and display capabilities.
Here is the fiddle sample.
Everything works well when the items are added directly using the html control. You may pickup some countries in the example above and click the view button to see that the code of the countries are well retrieved. However, I would like to populate the items another way. Precisely, I created a command to flush the observable array containing the selected items and force the first item in the list of available options to be selected (which is the country Laos in our example). This command is executed when clicking the second button.
After clicking this latter button, you can check that the observable selectedCountries contains the expected values by clicking the first button. Unfortunately, the UI control is not refreshed, do you have an idea how to do that? The html databiding for my view looks like
<select class="multi-select" data-bind="foreach: availableCountries,selectedOptions:selectedCountries" multiple="multiple">
<optgroup data-bind="attr: {label: label}, foreach: children">
<option data-bind="text: display, value: code"></option>
</optgroup>
</select>

The short answer is that Select2 doesn't know about changes you make to the underlying model.
I was able to make your sample work using a hack, see here: http://jsfiddle.net/bXPM6/
The changes made are:
<select id="foo" class="multi-select" data-bind="foreach: availableCountries, selectedOptions:selectedCountries" multiple="multiple">
(Note the added id=foo).
And I added a subscription to the observable:
function MyViewModel(){
var self = this;
self.availableCountries = ko.observableArray(app.availableCountries());
self.selectedCountries = ko.observableArray([]);
// added this bit
self.selectedCountries.subscribe(function (newValue) {
$('#foo').select2("val", newValue);
});
}
The better option is to make a custom knockout binding that can keep Select2 updated with changes to your model.
Something like this:
HTML:
<select class="multi-select" data-bind="foreach: availableCountries, selectedOptions:selectedCountries, select2: selectedCountries" multiple="multiple">
JavaScript:
ko.bindingHandlers.select2 = {
update: function (element, valueAccessor) {
$(element).select2("val", ko.unwrap(valueAccessor()) || "");
}
};
Hope this is of some help.

Selecting options from a drop down

I'm building a recipe-finder for a new food blog. The design I have basically involves the user selecting ingredients, one at a time, from a drop down <select>, the option disappearing from the list (so they can't select it again) and appearing on another HTML list with a link to remove it from the list. Once they're done, they click a button and that takes them through to a results page.
Here's the select markup as generated by the PHP:
<select>
<option value="">Please select</option>
<option value="beef-mince">Beef mince</option>
<option value="carrots">Carrots</option>
...
</select>
It's not drastically complex but it does raise a few questions on how I'm going to do some of these things. I'm using jquery.
I need to store the selected items in memory so I know what to send to the search page when they've done selecting items. What's the best way of doing that in your opinion as each item has two values (its "real" value and its database-value)?
How do I make "Please select" the selected option after they've selected something (preferable without triggering the onchange event)?
Once I've stored it in memory and added it to the displayed list of things they're searching for, how do I delete that item from the available items? Can I just "hide" or disable it (safely)?
If in #3 I have to delete it from the DOM, when I add it again, can I sort the list (based on either value) and keep the please-select option at the top?

1.) You can append hidden form elements to the page whose value is the value of the selected option.
2.)
jQuery("#select-list")[0].options[0].selected = true // assuming it's the first item
3.) I would remove the element from the DOM using jQuery("#select-list option:selected").remove()
4.) You can use before(). jQuery(your_default_option).before("#select-list option:first");

You can store the 'two values' in a hidden form field as an object in JSON notation. This will make it easy to modify in jQuery as the user interacts with the page.
You will need to use a combination of the onchange, keyup and keydown event to capture possible changes to the form so that you can re-select the 'Please Select' option.
You will need to remove the option from the dom and re-add it later. You can easily do this through jquery through something like this:
$("select option:selected").remove();
You can write a sorting function for the options starting with index 1, and keep the 'Please Select' as the first option.

1)
Basic idea, you need to check to make sure the first is not picked
var selections = [];
var mySel = document.getElementById("mySelectId");
var ind = mySel.selectedIndex;
selections.push( mySel.options[ind].value ); //add to a list for you to remember
mySel.options[ind] = null; //remove
2)
mySel.selectedIndex = 0;
3)
See #1
4) Yes you can add it anywhere you want by using insertBefore
Example here: http://www.pascarello.com/lessons/forms/moveSelectOptions.html

Will leave this answer here but I think I failed to read your whole post, so it might not help much.
You need to give your select a id like this:
<select id="MySelect">
<option value="">Please select</option>
<option value="beef-mince">Beef mince</option>
<option value="carrots">Carrots</option>
...
</select>
And to get it is just something like this:
<?php
$value = $_REQUEST["MySelect"];
echo $value;
?>
Code is not tested and $_REQUEST can be replaced by $_GET or $_POST regarding what you have specified as action on your form. $_REQUEST will eat it all though.