We Keep Coding

How to make an HTML attribute change depending on which option is selected

I am trying to make a button change when a certain option from a drop-down is selected.
document.getElementById("region").onchange = function() {
document.getElementById("order-btn").product-code = this.value;
}
<select name="option" id="option" required>
<option value="1234d1">Option 1</option>
<option value="amdk19">Option 2</option>
<option value="akd1sk">Option 3</option>
<option value="19sd91">Option 4</option>
<option value="asjd91">Option 5</option>
<option value="129e8j">Option 6</option>
</select>
<div class="btn-checkout">
<button id="order-btn" type="submit" product-code="">Checkout</button>
</div>
What I need to happen is when an option is chosen from the drop-down, the product code associated with that option is put into the product-code="HERE" on the button.
For example, If I chose Option 2 on the drop-down, its product code "amdk19" would then be put into the button like this:
<button id="order-btn" type="sumbit" product-code="amdk19">
I think this can be done with JavaScript, but I could not figure out how.
Thanks

Something like this should work! You can't set attributes on the object directly, like you tried -- instead, you have to use setAttribute on the button. You can use .value on the dropdown to get the value of the selected option.
document.getElementById("option").onchange = function() {
const btn = document.getElementById("order-btn");
// `this` refers to the dropdown, so you're getting the dropdown's selected value
btn.setAttribute("product-code", this.value);
}
document.getElementById("order-btn").onclick = function() {
// `this` refers to the button
console.log(this.getAttribute("product-code"));
}
<select name="option" id="option" required>
<option selected disabled>Select An Option</option>
<option value="1234d1">Option 1</option>
<option value="amdk19">Option 2</option>
<option value="akd1sk">Option 3</option>
<option value="19sd91">Option 4</option>
<option value="asjd91">Option 5</option>
<option value="129e8j">Option 6</option>
</select>
<div class="btn-checkout">
<button id="order-btn" type="submit" product-code="">Checkout</button>
</div>

As there are already answer to this. I would like to recommend you Jquery for easy dealing with javascript.
Include jquery cdn like this : Adding jquery CDN in HTML
Add id to your select and button. Adding Id in HTML
Then use jquery methods like this:
$("#optionsOfSomething").on("change",function(e){
$("#order-btn").attr("product-code",$(this).val());
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.0/jquery.min.js"></script>
<select name="option" id="optionsOfSomething" required>
<option value="1234d1">Option 1</option>
<option value="amdk19">Option 2</option>
<option value="akd1sk">Option 3</option>
<option value="19sd91">Option 4</option>
<option value="asjd91">Option 5</option>
<option value="129e8j">Option 6</option>
</select>
<div class="btn-checkout">
<button id="order-btn" type="submit" product-code="">Checkout</button>
</div>

Get the value of Select dropdown list when the value sent by the form and that appearing in the dropdown list are different

I have a form which has the following Select dropdown list.
<select name="some_options" id="some_options">
#foreach(options as option)
<option value="{{$option->id}}">{{$option->value}}</option>
#endforeach
</select>
Here , the data are being sent from the database via the Controller
The Select data look like this
<select name="some_options" id="some_options">
<option value="opt001">Value 1</option>
<option value="opt002">Value 2</option>
<option value="opt003">Value 3</option>
<option value="opt004">Value 4</option>
<option value="opt005">Value 5</option>
</select>
Now, I have another disabled field which should get the value once the user changes the select option
<div>
<input type="text" id="some_options_cng" disabled>
</div>
My Javascript code
var opt = $('#some_options').val();
$('#some_options').on('change',function(){
opt = $('#some_options').val();
$('#some_options_cng').val(opt);
});
Now, the value in the <disabled> input field shows as
opt001 or opt002 and so on.
I want to show values as
Value 1 or Value 2.
How do I do it?

This code will work.
$('#some_options').change(function(){
var opt = $("#some_options").find(":selected").text(); //This line of code is
//important
$('#some_options_cng').val(opt);
})
$(document).ready(function(){
$('#some_options').change(function(){
var opt = $("#some_options").find(":selected").text();
$('#some_options_cng').val(opt);
})
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<select name="some_options" id="some_options">
<option value="opt001">Value 1</option>
<option value="opt002">Value 2</option>
<option value="opt003">Value 3</option>
<option value="opt004">Value 4</option>
<option value="opt005">Value 5</option>
</select>
<div style="height:5px;"></div>
<div>
<input type="text" id="some_options_cng" disabled>
</div>

Automatically changing input values when selected a new element

How can I get input values to change dynamically when I select some element from select tag. I want in this input box to be shown a proper value when I change select option.
<select onchange="changevalue()" id="selectingg">
<option value="0">...</option>
<option value="1">Comedy</option>
<option value="2">Horror</option>
<option value="3">Action</option>
<option value="4">Sci-fi</option>
<option value="5">Adventure</option>
<option value="6">Documentary</option>
<option value="7">Anime</option>
</select>
<input type = "text" id="inputting"></input>

You could use addEventListener on change event and get the value from the event.target dropdown like so:
document.getElementById("dropdownCategory").addEventListener('change', event => document.getElementById('categorySelected').value = event.target.value);
<select id="dropdownCategory">
<option value="0">...</option>
<option value="1">Comedy</option>
<option value="2">Horror</option>
<option value="3">Action</option>
</select>
<input type="text" id="categorySelected"></input>

The below code is working fine for me you may try this code.
In below code I am assigning select value to input tag value.
function changevalue(){
document.getElementById("inputting").value =
document.getElementById("selecting").value;
}
<select onchange="changevalue()" id="selecting">
<option value="0">...</option>
<option value="1">Comedy</option>
<option value="2">Horror</option>
<option value="3">Action</option>
<option value="4">Sci-fi</option>
<option value="5">Adventure</option>
<option value="6">Documentary</option>
<option value="7">Anime</option>
</select>
<input type = "text" id="inputting"></input>

Selecting item from a dropdown with javascript

Here is a dropdown menu of a website
<select name="ctl00$ddlWersjeJezykowe" onchange="javascript:setTimeout('__doPostBack(\'ctl00$ddlWersjeJezykowe\',\'\')', 0)" id="ddlWersjeJezykowe" style="width:100px;margin-right: 10px;">
<option selected="selected" value="1">Polska</option>
<option value="2">English</option>
<option value="17">Русская</option>
<option value="19">Українська</option>
<option value="20">Deutsch</option>
<option value="21">Français</option>
<option value="22">Español</option>
<option value="24">Português</option>
<option value="25">Türk</option>
</select>
I want to change the language to English through browser console. I tried this on my console
document.getElementById("ddlWersjeJezykowe").value="2";
It only selects English but doesn't change the language. How can i change the language to English through my browser console?

Changing the value programmatically doesn't fire the onchange event, so you have to call setTimeout('__doPostBack(\'ctl00$ddlWersjeJezykowe\',\'\')', 0) too.
Alternatively, you can call document.getElementById("ddlWersjeJezykowe").onchange()

This is will get the selected value from select dropdown
<select id="language" style="width:100px;margin-right: 10px;">
<option selected="selected" value="1">Polska</option>
<option value="2">English</option>
<option value="17">Русская</option>
<option value="19">Українська</option>
<option value="20">Deutsch</option>
<option value="21">Français</option>
<option value="22">Español</option>
<option value="24">Português</option>
<option value="25">Türk</option>
</select>
function GetValue() {
var e = document.getElementById("language");
var result = e.options[e.selectedIndex].value;
document.getElementById("result").innerHTML = result;
}
<button type="button" onclick="GetValue()">Get Selected Value</button>
<div id="result"></div>

Links in <select> dropdown options

Is it possible for each dropdown options to link somewhere when selected without the need for an external button?
<select>
<option value="x">x</option>
<option value="y">y</option>
</select>

You can use the onChange property. Something like:
<select onChange="window.location.href=this.value">
<option value="www.google.com">A</option>
<option value="www.aol.com">B</option>
</select>

Add an onchange event handler and set the pages location to the value
<select id="foo">
<option value="">Pick a site</option>
<option value="http://www.google.com">x</option>
<option value="http://www.yahoo.com">y</option>
</select>
<script>
document.getElementById("foo").onchange = function() {
if (this.selectedIndex!==0) {
window.location.href = this.value;
}
};
</script>

... or if you want / need to keep your option 'value' as it was, just add a new attribute:
<select id="my_selection">
<option value="x" href="/link/to/somewhere">value 1</option>
<option value="y" href="/link/to/somewhere/else">value 2</option>
</select>
<script>
document.getElementById('my_selection').onchange = function() {
window.location.href = this.children[this.selectedIndex].getAttribute('href');
}
</script>

Maybe this will help:
<select onchange="location = this.value;">
<option value="home.html">Home</option>
<option value="contact.html">Contact</option>
<option value="about.html">About</option>
</select>

This is an old question, I know but for 2019 peeps:
Like above if you just want to change the URL you can do this:
<select onChange="window.location.href=this.value">
<option value="www.google.com">A</option>
<option value="www.aol.com">B</option>
</select>
But if you want it to act like an a tag and so you can do "./page", "#bottom" or "?a=567" use window.location.replace()
<select onChange="window.location.redirect(this.value)">
<option value="..">back</option>
<option value="./list">list</option>
<option value="#bottom">bottom</option>
</select>

Extending on #kevin's answer,
if someone has to perform some confirmation logic if URL is critical.
<select onChange=" this.options[this.selectedIndex].text == 'Delete' ? "Confirmation logic" : window.location.href=this.value;" >
<option selected disabled>Action</option>
<option value="/user/view">View</option>
<option value="/user/edit">Edit</option>
<option value="/user/delete">Delete</option>
</select>

You can use this code:
<select id="menu" name="links" size="1" onchange="window.location.href=this.value;">
<option value="URL">Book</option>
<option value="URL">Pen</option>
<option value="URL">Read</option>
<option value="URL">Apple</option>
</select>