Develop Reference

Why does my JS function only affect the first element addressed in the HTML structure? (changing display property of class)

my basic structure of the JS function works. However, it only affects the first DIV in the HTML structure that is to be shown and hidden.
The CSS class "map-content" has none as display property. Several containers will receive this class and will therefore initially be hidden. All DIV containers get their own value, which is necessary in my code when changing the display property.
This is my function, which basically works, but only shows and hides the first container (in the HTML structure) with the "map-content" class.
function validate_3() {
var x = document.getElementById("location_select");
var y = x.options[x.selectedIndex].value;
var a = document.querySelector(".map-content");
var b = a.getAttribute('value');
{
if (y == b) {
a.style.display = "block";
} else {
a.style.display = "none";
}
}
}
.map-content {
display: none;
}
<select id="location_select" onchange="validate_3">
<option disabled selected>Select location...</option>
<option value="de_germany">Berlin: Germany</option>
<option value="fr_france">Paris: France</option>
<option value="it_italy">Rome: Italy</option>
</select>
<div class="map-content" value="de_germany">
<h3>This is Berlin</h3>
<p>Berlin is in Germany</p>
</div>
<div class="map-content" value="fr_france">
<h3>This is Paris</h3>
<p>Paris is in France</p>
</div>
<div class="map-content" value="it_italy">
<h3>This is Rome</h3>
<p>Rome is in Italy</p>
</div>
Note on the code snippet: I don't know why, but unlike my test interface, none of the selections work here. Not even the first in the structure as described in the text.
I am happy to get general suggestions for a better structure if there are any.

you are missing a set of parentheses here onchange="validate_3"> , add a set of parentheses like this onchange="validate_3()">, and your first selection should work
To get what you want, make sure you've added the parentheses as shown above.
javascript,
// take this line out of your funtion and change `querySelector` to
//`querySelectorAll`
var a = document.querySelectorAll(".map-content");
function validate_3() {
var x = document.getElementById("location_select");
var y = x.options[x.selectedIndex].value;
//use The forEach() method to executes a provided function once for each
//element.
a.forEach((element) => {
if (y != element.getAttribute("value")) {
(element.classList.add("map-content"))
} else {
element.classList.remove("map-content")
};
});
};
But really, you're better off not using onclick at all and attaching the event handler to the DOM node through your Javascript code. This is known as unobtrusive javascript.

Tampermonkey: Hide Options in Dropdown if they don't contain a string

I am working on a Tampermonkey script to make life a lot easier. So picture this: There's a dropdown supplying 400+ options. However, I only need to use two of them. So all the others can be hidden.
So how do I do this? Currently, I am working with this, but it doesn't really do what I want it to.
var firstCampaignName = "001 - Campaign";
var secondCampaignName = "002 - Campaign";
These are the two options I want to keep. I halfway think I could simplify this by matching them both on " - Campaign" or something. Because the names are nigh-identical. But anyway. So here's the function I'm working with.
$('#dropdown option').each(function(){
if ('#dropdown option'.text() === firstCampaignName || '#brand option'.text() === secondCampaignName)
{
if ($.inArray($(this).text()))
$(this).show();
// If not, hide it
else
$(this).hide();
}
});
It's obvious that I'm doing something wrong. Somewhere in this, I am missing something. So, please, help?

To hide all options from the dropdown except the 2 specific options you can do the following. Note that as mentioned as comment by charlietfl that to hide options is not supported cross browser, so maybe it's an option for you to remove those options instead of hiding them as you mentioned that you don't need them.
var firstCampaignName = "001 - Campaign";
var secondCampaignName = "002 - Campaign";
$('#dropdown option').each(function() {
if ($(this).text() === firstCampaignName || $(this).text() === secondCampaignName) {
$(this).show();
} else {
$(this).hide();
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<select id="dropdown">
<option value="1">001 - Campaign</option>
<option value="2">002 - Campaign</option>
<option value="3">003</option>
<option value="4">004</option>
<option value="5">005</option>
</select>

Disabling an option from a selector so it can't be removed

I have a selector that looks like this:
<select id="patientSelect">
<option disabled selected style='display: none;' id="patient0">
Incoming Patients</option>
<option id="patient1"></option>
<option id="patient2"></option>
</select>
Because I kind of wanted a placeholder type text (i.e the first option) for the selector. And with my javascript I wanted it so that if the selected option was patient1 and you clicked a button it would be removed and would go back to showing the disabled 'Incoming Patients' thing. The javascript:
$(".ui-btn").click(function(){
remove();
$('#patientSelect :selected').attr('selected', '0');
$('#patientSelect').change();
});
function remove(){
var x = document.getElementById("patientSelect");
x.remove(x.selectedIndex);
}
Problem is it always removes more than 1 option, so if I got rid of "patient2" and tried to run remove() the list becomes a long blank list. All help is appreciated, please don't be too harsh. :P
Edit
Sorry, basically I want the text 'Incoming Patients' (which is the first option of my selector) to never be removed. No matter how many times 'function remove()' tries to run. It can remove the other options fine, just never the first one.
This may not even be possible, I'm not sure..
If there's another way to get text onto a selector without options that'd be fine too :-)
Maybe something like:
function remove(){
if(option != 1){
var x = document.getElementById("patientSelect");
x.remove(x.selectedIndex);
}
}

Try
var $ps = $('#patientSelect');
$(".ui-btn").click(function () {
var $sel = $ps.find('option:selected')
if ($sel.index() > 0) {
$sel.remove();
$ps.val($ps.find('option:eq(0)').val())
}
});
Demo: Fiddle

You can give this a try.
$(".uibtn").click(function(){
remove();
$('#patientSelect').append("<option disabled selected style='display: none;' id='patient0'>Incoming Patients</option>");
$('#patientSelect').change();
});
function remove(){
var x = document.getElementById("patientSelect");
x.remove(x.selectedIndex);
}
Check this http://jsfiddle.net/7yR5V/

Hiding Drop Down Boxes if Radio Button other than default is Clicked

I swear I'm going to learn more JavaScript...
I have this page (which really an include file in another ASP page, but I copied the correct HTML and made it so it'd load by itself for my testing purposes):
FO Samples
This is how it should show when they first load it. If they choose one of the other radio buttons, it should HIDE the 2 dropdown boxes. Using this code (something I found from someone else's question on here), its working.
<script type="text/javascript">
function ChangeDropdowns(value) {
if (value == "0") {
document.getElementById('SAMPLEDROPDOWN').style.display = 'block';
}
else {
document.getElementById('SAMPLEDROPDOWN').style.display = 'none';
}
}
</script>
But I can't figure out how to make it show them again if they go back to the "I wanna pick my own!" radio. The value of SAMPGROUP is the ID from the database of that sample category group. So it won't necessarily be in numerical order, it might skip #'s (if we delete a category or something). Basically, it should show the dropdowns if SAMPGROUP = 0 and not if its anything else!
I tried changing my code to this (95 being the value of SAMPGROUP for the "Autumm" option), but it doesn't seem to have made a difference.
<script type="text/javascript">
function ChangeDropdowns(value) {
if (value == "0") {
document.getElementById('SAMPLEDROPDOWN').style.display = 'block';
} else if (value == "95") {
document.getElementById('SAMPLEDROPDOWN').style.display = 'none';
}
else {
document.getElementById('SAMPLEDROPDOWN').style.display = 'none';
}
}
</script>
Any help would be greatly appreciated!!
Mahalo!

You are not setting the "value" in your onchange event, thus it's never equal to 0. Try changing this:
<input type="radio" name="SAMPGROUP" value="0" OnChange="Javascript:ChangeDropdowns()" checked />
to
<input type="radio" name="SAMPGROUP" value="0" OnChange="Javascript:ChangeDropdowns(0)" checked />
Here is the fiddle.
Good luck.

You may not be passing any value to the parameter "value" on calling the function ChangeDropdowns. Please ensure you pass the value like ChangeDropdowns(0) etc..

How to avoid the need for ctrl-click in a multi-select box using Javascript?

I thought this would be a simple hack, but I've now been searching for hours and can't seen to find the right search term. I want to have an ordinary multiple select box (<select multiple="multiple">) except I don't want the user to have to hold down the control key to make multiple selections.
In other words, I want a left click to toggle the <option> element that's under the cursor without changing any of the others. In other other words, I want something that looks like a combo list box but behaves like a group of check boxes.
Can anybody suggest a simple way to do this in Javascript? Thanks.

Check this fiddle: http://jsfiddle.net/xQqbR/1022/
You basically need to override the mousedown event for each <option> and toggle the selected property there.
$('option').mousedown(function(e) {
e.preventDefault();
$(this).prop('selected', !$(this).prop('selected'));
return false;
});
For simplicity, I've given 'option' as the selector above. You can fine tune it to match <option>s under specific <select> element(s). For ex: $('#mymultiselect option')

Had to solve this problem myself and noticed the bugged behavior a simple interception of the mousedown and setting the attribute would have, so made a override of the select element and it works good.
jsFiddle: http://jsfiddle.net/51p7ocLw/
Note: This code does fix buggy behavior by replacing the select element in the DOM. This is a bit agressive and will break event handlers you might have attached to the element.
window.onmousedown = function (e) {
var el = e.target;
if (el.tagName.toLowerCase() == 'option' && el.parentNode.hasAttribute('multiple')) {
e.preventDefault();
// toggle selection
if (el.hasAttribute('selected')) el.removeAttribute('selected');
else el.setAttribute('selected', '');
// hack to correct buggy behavior
var select = el.parentNode.cloneNode(true);
el.parentNode.parentNode.replaceChild(select, el.parentNode);
}
}
<h4>From</h4>
<div>
<select name="sites-list" size="7" multiple>
<option value="site-1">SITE</option>
<option value="site-2" selected>SITE</option>
<option value="site-3">SITE</option>
<option value="site-4">SITE</option>
<option value="site-5">SITE</option>
<option value="site-6" selected>SITE</option>
<option value="site-7">SITE</option>
<option value="site-8">SITE</option>
<option value="site-9">SITE</option>
</select>
</div>

techfoobar's answer is buggy, it unselects all options if you drag the mouse.
Sergio's answer is interesting, but cloning and removing events-bound to a dropdown is not a nice thing.
Try this answer.
Note: Doesn't work on Firefox, but works perfectly on Safari/Chrome/Opera. (I didn't test it on IE)
EDIT (2020)
After 5 years since my original answer, I think best practice here is to replace the dropdown with checkboxes. Think about it, that's the main reason why checkboxes exist in the first place, and it works nicely with old browsers like IE & modern mobiles without any custom JS to handle all the wacky scenarios.

Necromancing.
The selected answer without jQuery.
Also, it missed setting the focus when an option is clicked, because you have to do this yourself, if you write e.preventDefault...
Forgetting to do focus would affect CSS-styling, e.g. bootstrap, etc.
var options = [].slice.call(document.querySelectorAll("option"));
options.forEach(function (element)
{
// console.log("element", element);
element.addEventListener("mousedown",
function (e)
{
e.preventDefault();
element.parentElement.focus();
this.selected = !this.selected;
return false;
}
, false
);
});

I had same problem today, generally the advice is to use a list of hidden checkboxes and emulate the behavior via css, in this way is more easy to manage but in my case i don't want to modify html.
At the moment i've tested this code only with google chrome, i don't know if works with other browser but it should:
var changed;
$('select[multiple="multiple"]').change(function(e) {
var select = $(this);
var list = select.data('prevstate');
var val = select.val();
if (list == null) {
list = val;
} else if (val.length == 1) {
val = val.pop();
var pos = list.indexOf(val);
if (pos == -1)
list.push(val);
else
list.splice(pos, 1);
} else {
list = val;
}
select.val(list);
select.data('prevstate', list);
changed = true;
}).find('option').click(function() {
if (!changed){
$(this).parent().change();
}
changed = false;
});
Of course suggestions are welcome but I have not found another way

Reusable and Pure JavaScript Solution
const multiSelectWithoutCtrl = ( elemSelector ) => {
let options = document.querySelectorAll(`${elemSelector} option`);
options.forEach(function (element) {
element.addEventListener("mousedown",
function (e) {
e.preventDefault();
element.parentElement.focus();
this.selected = !this.selected;
return false;
}, false );
});
}
multiSelectWithoutCtrl('#mySelectInput') /* Can use ID or Class */
option {
font-size: 20px;
padding: 10px 20px;
}
<select multiple id="mySelectInput" class="form-control">
<option>🍎 Apple</option>
<option>🍌 Banana</option>
<option>🍍 Pineapple</option>
<option>🍉 Watermelon</option>
</select>