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How to refresh a select list in html

I have a drop-down list where depending on the selected value, the next drop-down list shows specific values. when changing the value of the first list and then going back to the old value, the second list does not update. keeps the same value selected before. How can I make the second list update to the value I marked as selected by default whenever I change the value of the first list?
I hope you guys were able to understand me, and I thank you for your time.
Here's the code:
<select onchange="showprd('hidevalue', this), showprd2('hidevalue2', this)">
<option value="" disabled selected hidden>Selecione</option>
<option value="0">São Francisco</option>
<option value="1">Bradesco</option>
</select>
<br>
<br>
<select hidden id="hidevalue">
<option value="" disabled selected hidden>Selecione o produto</option>
<option value="pleno">Pleno</option>
<option value="integrado">Integrado</option>
</select>
<select hidden id="hidevalue2">
<option value="" disabled selected hidden>Selecione o produto</option>
<option value="junior">Junior</option>
<option value="senior">Senior</option>
</select>
</body>
<script>
function showprd(id, elementValue) {
document.getElementById(id).style.display = elementValue.value == 0 ? 'block' : 'none';
}
function showprd2(id, elementValue) {
document.getElementById(id).style.display = elementValue.value == 1 ? 'block' : 'none';
}
</script>

TL;DR. Control the input value changes in one place.
Please see the updated snippet below. html structure hasn't been changed, but I've removed the inline js call and updated the id names. JavaScript blocks are commented in details.
In a nut-shell, this code listens for any change to the parent select dropdown. Whenever a change occurs, its child dropdowns will reset their values and toggle their visibility accordingly.
// Assign each dom element to a variable
const primarySelect = document.querySelector('#primary');
const childSelect1 = document.querySelector('#child1');
const childSelect2 = document.querySelector('#child2');
const defaultValues = document.querySelectorAll('.default');
function resetInputs() {
// Reset the child select options to default
defaultValues.forEach(option => option.selected = true);
}
function handlePrimary(e) {
// Reset the child select values whenever the parent value changes
resetInputs();
// `input` value is always a string. Here we're converting it to a number
const val = parseFloat(e.target.value);
// Toggle visibility of child select dropdowns
[childSelect1, childSelect2].
forEach((select, i) => select.style.display = val === i ? 'block' : 'none');
}
primarySelect.addEventListener('change', handlePrimary);
<select id="primary">
<option value="" disabled selected hidden>Selecione</option>
<option value="0">São Francisco</option>
<option value="1">Bradesco</option>
</select>
<br>
<br>
<select hidden id="child1">
<option class="default" value="" disabled selected hidden>Selecione o produto</option>
<option value="pleno">Pleno</option>
<option value="integrado">Integrado</option>
</select>
<select hidden id="child2">
<option class="default" value="" disabled selected hidden>Selecione o produto</option>
<option value="junior">Junior</option>
<option value="senior">Senior</option>
</select>

If I understood correctly, the expected behavior is when the second or third <select> is hidden, the <select> should go back to default (the first <option>?). If so, then remove disabled and hidden from the first <option> of the second and third <select> then add the following:
selectObj.hidden = true;
selectObj.selectedIndex = 0;
The example below has a <form> wrapped around everything (always use a form if you have more than one form control. By using HTMLFormElement interface I rewrote the code and can reference all form controls with very little code. Inline event handlers are garbage so don't do this:
<select id='sel' onchange="lame(this)">
Instead do this:
selObj.onchange = good;
OR
selObj.addEventListener('change', better)
Read about events and event delegation
const UI = document.forms.UI;
UI.onchange = showSelect;
function showSelect(e) {
const sel = e.target;
const IO = this.elements;
if (sel.id === "A") {
if (sel.value === '0') {
IO.B.hidden = false;
IO.C.hidden = true;
IO.C.selectedIndex = 0;
} else {
IO.B.hidden = true;
IO.B.selectedIndex = 0;
IO.C.hidden = false;
}
}
}
<form id='UI'>
<select id='A'>
<option disabled selected hidden>Pick</option>
<option value="0">0</option>
<option value="1">1</option>
</select>
<br>
<br>
<select id="B" hidden>
<option selected>Pick B</option>
<option value="0">0</option>
<option value="1">1</option>
</select>
<select id="C" hidden>
<option selected>Pick C</option>
<option value="0">0</option>
<option value="1">1</option>
</select>
</form>

I give you an example for your reference:
let secondList = [
[{
value: "pleno",
text: "Pleno"
},
{
value: "integrado",
text: "Integrado"
}
],
[
{
value: "junior",
text: "Junior"
},
{
value: "senior",
text: "Senior"
}
]
]
function update(v){
let secondSelectBox=document.getElementById("second");
secondSelectBox.style.display="none";
let optionList=secondList[v.value];
if (optionList){
let defaultOption=new Option("Selecione o produto","");
secondSelectBox.innerHTML="";
secondSelectBox.options.add(defaultOption);
optionList.forEach(o=>{
let vv=new Option(o.text,o.value);
secondSelectBox.options.add(vv);
})
secondSelectBox.style.display="block";
}
}
<select onchange="update(this)">
<option value="" disabled selected hidden>Selecione</option>
<option value="0">São Francisco</option>
<option value="1">Bradesco</option>
</select>
<select hidden id="second">
</select>

Change text within Label to option from selection menu

This my custom select menu:
<select name="bankSelect" id="bankSelect" onchange="dispchange(this.form.bankSelect)">
<option>EQUIFAX</option>
<option value = 5 >EQUIFAX</option>
<option value = 6>TRANSUNION</option>
<option value = 7>EXPERIAN</option>
<option value = 8>BANK OF AMERICA</option>
<option value = 9>WELLS FARGO</option>
<option value = 10>CITIBANK</option>
<option value = 11>JPMORGAN</option>
<option value = 12>NAVIENT</option>
<option value = 13>CAPITAL ONE</option>
<option value = 14>U.S BANCORP</option>
</select>
This is my label:
<div class="info">
<label>Bank: </label>
<label id="bank">EQUIFAX</label><br>
</div>
I need to change the text within label with the ID='bank to the option i select from the menu i above.
So if i pick the option with value 9, then my label should change the text it's displaying by defualt,'EQUIFAX' to then display 'WELLS FARGO'.
This is what I've tried in my java-script based on googling similar questions:
function dispchange(bankSelect) {
var bsel_index = bankSelect.selectedIndex;
var bselin = bankSelect.options[bsel_index].value;
if(bselin == '6')
document.getElementById("bank").innerHTML = 'Transunion';
else if(opcao == '1')
document.getElementById('complemento').innerHTML = 'Titulo';
}
It does nothing. What am I doing wrong? Is there a better way / another way to change the label? Can I use something other than a label to display my choice from the selection menu? If so, how do I ensure is always displays the choice currently selected?

use option.text instead of option.value:
function dispchange() {
var el = document.getElementById('bankSelect');
document.getElementById('bank').innerHTML = el.options[el.selectedIndex].text;
}
<select name="bankSelect" id="bankSelect" onchange="dispchange()">
<option>EQUIFAX</option>
<option value="5">EQUIFAX</option>
<option value="6">TRANSUNION</option>
<option value="7">EXPERIAN</option>
<option value="8">BANK OF AMERICA</option>
<option value="9">WELLS FARGO</option>
<option value="10">CITIBANK</option>
<option value="11">JPMORGAN</option>
<option value="12">NAVIENT</option>
<option value="13">CAPITAL ONE</option>
<option value="14">U.S BANCORP</option>
</select>
<div class="info">
<label>Bank: </label>
<label id="bank">EQUIFAX</label><br>
</div>

function dispchange(bankSelect) {
console.log(document.getElementById("bankSelect").value)
document.getElementById('bank').innerHTML = document.getElementById("bankSelect").value;
}
<select name="bankSelect" id="bankSelect" onchange="dispchange()">
<option value="EQUIFAX">EQUIFAX</option>
<option value="TRANSUNION">TRANSUNION</option>
<option value ="EXPERIAN">EXPERIAN</option>
<option value= "BANK OF AMERICA">BANK OF AMERICA</option>
<option value ="WELLS FARGO">WELLS FARGO</option>
</select>
<div class="info">
<label>Bank: </label>
<label id="bank">EQUIFAX</label><br>
</div>
If you can change the value of the options from number to the Bank name then the following code is going to work as you need.
Otherwise, you have to create an array or object with the numbers and Bank names.
Is the above code work for you?

How to get the OPTION's TEXT value

In this case, only primary dropdown will change, other dropdowns' values will change automatically according to it (so users wont be changing them) I'm trying to get the Option's TEXT value using PHP with $_POST. But i can only get it when i manually changed the other dropdown .
I have tried to use the trigger() method, but it fails to get the option text value. Any idea why the code fails to work. Thank you.
function setDropDown() {
var index_name =
document.getElementsByName('ForceSelection')[0].selectedIndex;
var others = document.querySelectorAll('.secondary');
for (var i = 0; i < others.length; i++) {
others[i].selectedIndex = index_name;
}
}
<!-- try to get the option text value and pass it to input field-->
<!-- Then in the php code use $_POST[] to retrieve the input value-->
function setTextField(ddl) {
document.getElementById('make_text').value = ddl.options[ddl.selectedIndex].text;
}
$("select").trigger("change");
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<form action="" method="post">
<div><b>Primary dropdown:</b>
<select name="ForceSelection" id="ForceSelection" onChange="javascript:return setDropDown();">
<option value="" selected>Select</option>
<option value="treatmentid1">treatmentname1</option>
<option value="treatmentid2">treatmentname2</option>
</select>
</div>
<div>
<b>Other dropdown 1</b>:
<select class='secondary' id="Qualifications" name="Qualifications" onChange="setTextField(this)">
<option value="select">select</option>
<option value="treatmentid1">treatmentname1</option>
<option value="treatmentid2">treatmentname2</option>
</select></div>
<input id="make_text" type="hidden" name="make_text" value="" />
<div> <b>Other dropdown 2</b>:
<select class='secondary' id="Qualifications2" name="Qualifications2">
<option value="select">select</option>
<option value="treatmentid1">treatmentname1</option>
<option value="treatmentid2">treatmentname2</option>
</select>
</form>
PHP Code
$value =$_POST['make_text'];

Html element <select> onchange doesn't fire for programmatic changes, you need to fire it yourself with
$(".secondary").trigger("change");
or by Id
$("#Qualifications").trigger("change");
The problem is that your hidden <input> never had the value. if you remove the hidden it on your code you can check it.
So when you POSTED the values the value on make_text was empty string. So if you fire the trigger after the for loop then it will work.
function setDropDown() {
var index_name = document.getElementsByName('ForceSelection')[0].selectedIndex;
var others = document.querySelectorAll('.secondary');
for (var i = 0; i < others.length; i++) {
others[i].selectedIndex = index_name;
}
$("#Qualifications").trigger("change");
}
function setTextField(ddl) {
document.getElementById('make_text').value = ddl.value;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<form action="" method="post">
<div><b>Primary dropdown:</b>
<select name="ForceSelection" id="ForceSelection" onChange="javascript:return setDropDown();">
<option value="" selected>Select</option>
<option value="treatmentid1">treatmentname1</option>
<option value="treatmentid2">treatmentname2</option>
</select>
</div>
<div>
<b>Other dropdown 1</b>:
<select class='secondary' id="Qualifications" name="Qualifications" onChange="setTextField(this)">
<option value="select">select</option>
<option value="treatmentid1">treatmentname1</option>
<option value="treatmentid2">treatmentname2</option>
</select></div>
<input id="make_text" name="make_text" value="" />
<div> <b>Other dropdown 2</b>:
<select class='secondary' id="Qualifications2" name="Qualifications2">
<option value="select">select</option>
<option value="treatmentid1">treatmentname1</option>
<option value="treatmentid2">treatmentname2</option>
</select>
</form>

I have to say that I don't see any need to use a hidden input text to POST data to PHP because you can just post the value of the <select> and retrieve it in PHP like this $force = $_POST["ForceSelection"];.
Otherwise, if you want to continue what you started, you can change your setDropDown() function to this :
function setDropDown() {
#Get the selected value of the ForceSelection select :
var index_name = $('#ForceSelection').val();
#Change the value of the other secondary select :
$(".secondary").each(function( index ) {
$(this).val(index_name).change();//This will change the value and trigger the change event.
});
}

Pass dropdown values to text box with javascript

I don't know much about javascript and unfortunately don't have time to learn before this project is due (wish I did!). I assume it is possible to pass the value of a drop-down selection into a hidden text input field on a form before the form is submitted. Could anyone help me figure out how to do that with javascript? Thank you! Here are my drop-down and text box details:
<div class="formEntryArea">
<div class="formEntryLabel">
<span class="formLabel"><label for=" langdropdown">Would you like to receive library notices in English or Spanish? ><span class="formRequired">*</span></label></span>
</div>
<div class="formMultiSelect" id=”langdropdown”>
<select name=" langdropdown ">
<option value="0" selected="selected">Choose language</option>
<option value="eng">English</option>
<option value="spa">Spanish</option>
<input type="text" id="ddepartment" name="ddepartment" value=””>
</select>
</div>

This is simply. First of all, you have to bind a change event handler for your select. Then, you have to set input text with value selected from dropdown.
var select=document.getElementsByTagName('select')[0];
var input=document.getElementById('ddepartment');
select.onchange=function(){
input.value=select.options[select.selectedIndex].text;
}
<div class="formEntryArea">
<div class="formEntryLabel">
<span class="formLabel"><label for=" langdropdown">Would you like to receive library notices in English or Spanish? ><span class="formRequired">*</span></label></span>
</div>
<div class="formMultiSelect" id=”langdropdown”>
<select name=" langdropdown ">
<option value="0" selected="selected">Choose language</option>
<option value="eng">English</option>
<option value="spa">Spanish</option>
</select>
<input type="text" id="ddepartment" name="ddepartment">
</div>

You can use this code:
var myselect = document.getElementById("MySelect");
myselect.onchange = function(){
alert(myselect.options[myselect.selectedIndex].value);
document.getElementById("ddepartment").value = myselect.options[myselect.selectedIndex].value;
};
Result: https://jsfiddle.net/fh5myefw/

Mind to close the tags, it's better practice.
var select = document.getElementById('selectElem');
var outputElem = document.getElementById('ddepartment');
select.addEventListener('change',function(){
var newValue = !this.selectedIndex ? "":this.options[this.selectedIndex].text;
outputElem.value = newValue;
});
<select name="langdropdown" id="selectElem" required>
<option value="" selected="selected">Choose language</option>
<option value="eng">English</option>
<option value="spa">Spanish</option>
</select>
<input type="text" id="ddepartment" name="ddepartment" value="">

this is javascript function
function func(selectObject)
{
document.getElementById('ddepartment').value = selectObject.value;
}
add onchange event to select element like this
<select name="langdropdown" onchange="func(this)">

Here use this:
var sel = document.getElementById('lang');
sel.onchange = function() {
var val = this.options[this.selectedIndex].value;
var che = document.getElementById('cache').value;
che = val;
console.log(che);
}
SNIPPET
var sel = document.getElementById('lang');
sel.onchange = function() {
var val = this.options[this.selectedIndex].value;
var che = document.getElementById('cache').value;
che = val;
console.log(che);
}
<select id='lang' name="lang">
<option value="" selected>Choose language</option>
<option value="eng">English</option>
<option value="spa">Spanish</option>
<option value="jpn">Japanese</option>
<option value="zho">Chinese</option>
<option value="fin">Finnish</option>
<option value="nav">Navajo</option>
</select>
<input type="hidden" id="cache" name="cache" value=””>

Get value from select tag on javascript

I want to change the <img src> with value from my <select>.
I have the next HTML code:
<img id="fotosel" /><br/>
<select id="cmbfotos" onchange="aplicarFoto()">
<option value="gokussj3.jpg">Goku SSJ3</option>
<option value="gokussj4.jpg">Goku SSJ4</option>
<option value="gohanssj2.jpg">Gohan SSJ2</option>
<option value="gotenks.jpg">Super Gotenks</option>
<option value="krilin.jpg">Krilin</option>
</select>
and Javascript code:
var fotosel = document.getElementById("fotosel");
var cmb = document.getElementById("cmbfotos");
function aplicarFoto(){
fotosel.src = "fotos/"+cmb.options[cmb.selectedIndex].value;
}
But that doesnt work. I made a test putting an alert() with cmb.options[cmb.selectedIndex].value and nothing appears.
Some guess? Thank you!

Change your aplicarFoto() function to:
function aplicarFoto(_src) {
fotosel.src = 'fotos/' + _src;
}
and in your HTML:
<select id="cmbfotos" onchange="aplicarFoto(this.value)">
...
</select>

Try this
<img id="fotosel" /><br/>
<select id="cmbfotos" onchange="aplicarFoto(this.value)">
<option value="gokussj3.jpg">Goku SSJ3</option>
<option value="gokussj4.jpg">Goku SSJ4</option>
<option value="gohanssj2.jpg">Gohan SSJ2</option>
<option value="gotenks.jpg">Super Gotenks</option>
<option value="krilin.jpg">Krilin</option>
</select>
Javascipt :
var fotosel = document.getElementById("fotosel");
function aplicarFoto(elmImage){
fotosel.src = "fotos/"+elmImage;
}