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using jQuery to get selected value from form

I have a form that has a select field defined like this
The myName[] is like that because there are several repetitions in the sign-up form (the user first defines how many he wants to enter, and then that many forms are generated)
Now I would like to get the selected value using jQuery whenever somethign is selected, but as expected, it won't work: it's trying to get the info from an id, and there's more than one of this id. The result is that it's always getting the content of the first select field with the id it finds. I tried changing the id to a class, but that didn't work.
So how can I get the selected value of the select box that's actually triggering the event?
$(document).ready(function() {
$('#idOfmyName').change(function() {
var naam = $(this).find("option:selected").attr('value');
alert(naam);
});
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<select name="myname[]" id="idOfmyName">
<option value="jack">Jack</option>
<option value="rose">Rose</option>
</select>

Why can't you just use $(this).val(), if you want the selected Element?
But yes, when you've got multiple of the same ID, jQuery will over ever select the first one it finds - Though you do seem to know this; I've changed it to a class in this demo
$(document).ready(function() {
$('.idOfmyName').on('change', function() {
alert($(this).val());
});
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<select name="myname[]" class="idOfmyName">
<option value="jack">Jack</option>
<option value="rose">Rose</option>
</select>
<select name="myname[]" class="idOfmyName">
<option value="harry">Harry</option>
<option value="sally">Sally</option>
</select>
<select name="myname[]" class="idOfmyName">
<option value="edward">Edward </option>
<option value="vivian">Vivian </option>
</select>

for multiple you can do something like this
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<select name="myname[]" class="idOfmyName">
<option value="jack">Jack</option>
<option value="rose">Rose</option>
</select>
<select name="myname[]" class="idOfmyName">
<option value="jack">Jack</option>
<option value="rose">Rose</option>
</select>
<script>
$(document).ready(function() {
var names = [];
$('.idOfmyName').change(function() {
var naam = $(this).find("option:selected").attr('value');
if($.inArray(naam,names)){
names.push(naam);
}
alert(names);
});
});
</script>

Vanilla JavaScript way to get selected value using onchange method
function getSelectedValue(val) {
alert(val);
}
<select name="myname[]" onchange="getSelectedValue(this.value)">
<option value="jack">Jack</option>
<option value="rose">Rose</option>
</select>
<select name="myname[]" onchange="getSelectedValue(this.value)">
<option value="harry">Harry</option>
<option value="sally">Sally</option>
</select>

I need to keep the default option in #city with this code

Looking for a cascading dropdown i found this piece of code here, which is working almost perfect for me, but i need to keep the default option in the second select-menu after changing the value in the first one.
https://stackoverflow.com/a/28902561/10391817
function filterCity() {
var province = $("#province").find('option:selected').text(); // stores province
$("#option-container").children().appendTo("#city"); // moves <option> contained in #option-container back to their <select>
var toMove = $("#city").children("[data-province!='" + province + "']"); // selects city elements to move out
toMove.appendTo("#option-container"); // moves city elements in #option-container
$("#city").removeAttr("disabled"); // enables select
};
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<select class="select" id="province" onchange="filterCity();">
<option value="1">RM</option>
<option value="2">FI</option>
</select>
<select class="select" id="city" disabled>
<option>SELECT CITY</option>
<option data-province="RM" value="1">ROMA</option>
<option data-province="RM" value="2">ANGUILLARA SABAZIA</option>
<option data-province="FI" value="3">FIRENZE</option>
<option data-province="FI" value="4">PONTASSIEVE</option>
</select>
<span id="option-container" style="visibility: hidden; position:absolute;"></span>

You can try this code.
<select class="select" id="province">
<option value="1">RM</option>
<option value="2">FI</option>
</select>
<select class="select" id="city" disabled>
<option data-province="DEF">SELECT CITY</option>
<option data-province="RM" value="1">ROMA</option>
<option data-province="RM" value="2">ANGUILLARA SABAZIA</option>
<option data-province="FI" value="3">FIRENZE</option>
<option data-province="FI" value="4">PONTASSIEVE</option>
</select>
<span id="option-container" style="visibility: hidden; position:absolute;"></span>
<script>
$('#province').on('change', function() {
var province = $("#province").find('option:selected').text();
$("#city option[data-province!='" + province + "']").hide();
$("#city option[data-province='" + province + "']").show();
$("#city option[data-province='DEF'").show().prop('selected', true);
$("#city").removeAttr("disabled");
});
</script>
https://jsfiddle.net/sg0t23bc/5/

How to Select Dropdown hidden option with Jquery Selector?

<select class="form-control" id="prodname" name="pname" >
<option value="0" disabled="disabled" selected="selected">-- Select Product --</option>
#{
foreach(var product in (List<tbleProdcutDetail>)ViewBag.productlist)
{
<option value="#product.Id">#product.Product_Name</option>
<option hidden>#product.Quantity</option>
}
}
</select>
I want to select this option.
<option hidden>#product.Quantity</option>
I have tried this selector but could not get text.
var productunitprice = $("#prodname option").find("hidden").text();

You can use var text = $("option:selected",this).next().text() Example below.
$("#prodname").change(function() {
var text = $("option:selected",this).next().text()
console.log(text)
})
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<select id="prodname">
<option value="1">1</option>
<option hidden>1.1</option>
<option value="2">2</option>
<option hidden>2.2</option>
</select>

As an alternative to adding many unused and hidden options.
You can add the unit price to the relevant option directly using a data attribute for example data-unit-price.
foreach(var product in (List<tbleProdcutDetail>)ViewBag.productlist)
{
<option value="#product.Id" data-unit-price="#product.Quantity">#product.Product_Name</option>
}
Then simply read it from the selected option. In my humble opinion it is cleaner and doesn't use additional hidden option elements as storage for data belonging to other options.
$(document).ready(function() {
$("#prodname").change(function() {
var productunitprice = $("option:selected", this).data('unitPrice')
console.log(productunitprice)
})
})
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<select class="form-control" id="prodname" name="pname">
<option value="1" data-unit-price="5.25">product 45</option>
<option value="2" data-unit-price="12.99">product 94</option>
</select>

Drop down changes automatically ( vise versa would be best )

I need to change the 3rd field automatically depending on first two field. ( it would be best if I change 3rd field and then first 2 fields changes also )
I need a Jquery solution. Anyone can help me please?
<select id="First">
<option val="car">car</option>
<option val="phone">phone</option>
</select>
<select id="Second">
<option val="car">car</option>
<option val="phone">phone</option>
<option val="boll">boll</option>
</select>
<hr>
<select id="ChangeItAutomatically">
<option val="carcar">car car</option>
<option val="carphone">car phone</option>
<option val="carboll">car boll</option>
<option val="phonecar">phone car</option>
<option val="phonephone">phone phone</option>
<option val="phonecarboll">phone boll</option>
</select>

Is this what you're looking for?
$(document).ready(function() {
// on change for the 3rd select
$("#ChangeItAutomatically").on("change", function() {
// get the value and split on space
var value = $(this).val().split(" ");
// select the other two selects based on the values
$("#First").val(value[0]);
$("#Second").val(value[1]);
});
// on change for the first two selects
$("#First, #Second").on("change", function() {
// set the value of the 3rd select based on the combination of values of the first two
$("#ChangeItAutomatically").val($("#First").val() + " " + $("#Second").val());
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<select id="First">
<option val="car">car</option>
<option val="phone">phone</option>
</select>
<select id="Second">
<option val="car">car</option>
<option val="phone">phone</option>
<option val="boll">boll</option>
</select>
<hr>
<select id="ChangeItAutomatically">
<option val="car car">car car</option>
<option val="car phone">car phone</option>
<option val="car boll">car boll</option>
<option val="phone car">phone car</option>
<option val="phone phone">phone phone</option>
<option val="phone boll">phone boll</option>
</select>

JQuery Mobile CSS for dropdown menus

Here is a JSFiddle:
https://jsfiddle.net/7jknnn2n/
HTML:
<select class="base-choice">
<option value="English">English</option>
<option value="Spanish">Spanish</option>
</select>
<label class="contrastText" for="user_natives_language">Native Language</label>
<select class="first-choice" id="user_natives_language" name="user[natives_language]">
<option value="English">English</option>
<option value="Spanish">Spanish</option>
</select>
<label class="contrastText" for="user_next_language">I Want To Learn</label>
<select class="second-choice" id="user_next_language" name="user[next_language]">
<option value="Spanish">Spanish</option>
</select>
JS:
var $secondOption = $('.base-choice>option').clone();
$(".first-choice").change(function () {
var userSelected = $(this).val();
$('.second-choice').html($secondOption);
$('.second-choice option[value="' + userSelected + '"').remove()
});
CSS:
.base-choice{
display:none !important;
}
What I would like to do with the above JSFiddle is make it such that the .base-choice dropdown selector is hidden completely from the results portion of the fiddle. Also, when I toggle the Native Language dropdown and select something different you can see that the option for the I want to learn dropdown is no longer bolded. Any thoughts on how to fix this.

Since there is no way in CSS to select parent element you must use javascript.
In this updated fiddle I just found the select with base-choice and set the parent element (surrounding div) to also display:none.
$(".base-choice").parent().addClass("invisible");
https://jsfiddle.net/7jknnn2n/4/

Here is an updated fiddle https://jsfiddle.net/RachGal/7avurszn/1
var $secondOption = $('.base-choice>option').clone();
$(".first-choice").change(function () {
var userSelected = $(this).val();
$('.second-choice').html($secondOption);
$('.second-choice option[value="' + userSelected + '"').remove()
});
#select-3-button {
display:none!important;
padding:0!important;
opacity:0!important!;
}
.first-choice, .second-choice{opacity:.5; font-weight:normal;}
<script src="http://code.jquery.com/mobile/1.4.2/jquery.mobile-1.4.2.js"></script>
<select class="base-choice">
<option value="English">English</option>
<option value="Spanish">Spanish</option>
</select>
<label class="contrastText" for="user_natives_language">Native Language</label>
<select class="first-choice" id="user_natives_language" name="user[natives_language]">
<option value="English">English</option>
<option value="Spanish">Spanish</option>
</select>
<label class="contrastText" for="user_next_language">I Want To Learn</label>
<select class="second-choice" id="user_next_language" name="user[next_language]">
<option value="Spanish">Spanish</option>
</select>