Develop Reference

When registering both onchange and onclick on a select, the click event is triggered twice

Goal: Have a select whose option have nested structure when user clicks on the select, but when user selects an option the option should be displayed "normally" (ie with no leading spaces).
Attempted solution using JS and Jquery: My JS is far from sophisticated so I apologize in advance :)
I attempted to use .on("change") and .on("click") to change the selected option value (by calling .trim() since I achieve the "nested" structure with ). I'm also storing the original value of the selected option because I want to revert the select menu to its original structure in case the user selects another option.
The problem: The function registered for .on("click") is called twice, thus the select value immediately resets itself to its original value.
I suspect there is a much, much easier solution using CSS. I will be happy to accept an answer that will suggest such solution.
JSFiddle: https://jsfiddle.net/dv6kky43/9/
<form>
<select id="select">
<option value=""></option>
<option value="a"> a</option>
<option value="b"> b</option>
</select>
</form>
<textarea id="output"/>
var orig;
var output = $("#output");
output.val("");
function onDeviceSelection(event){
output.val(output.val() + "\nonDeviceSelection");
var select = event.target;
orig = select.selectedOptions[0].text;
select.selectedOptions[0].text = select.selectedOptions[0].text.trim()
}
function resetDeviceSelectionText(event) {
output.val(output.val() + "\nresetDeviceSelectionText");
var select = event.target;
if (orig !== undefined){
select.selectedOptions[0].text = orig;
}
}
$("#select").on("change", onDeviceSelection);
$("#select").on("click", resetDeviceSelectionText);

If you are already using jQuery, why not utilize data function to store the original value. This way you will also be able to specify different nest levels.
(function($){
$(document).on('change', 'select', function(event) {
$(this).find('option').each(function(index, element){
var $option = $(element);
// Storing original value in html5 friendly custom attribute.
if(!$option.data('originalValue')) {
$option.data('originalValue', $option.text());
}
if($option.is(':selected')) {
$option.html($option.data('originalValue').trim());
} else {
$option.html($option.data('originalValue'));
}
})
});
})(jQuery);
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<form>
<select id="select">
<option value=""></option>
<option value="a"> a</option>
<option value="b"> b</option>
</select>
</form>
Once caveat I see is, the selected option will appear trimmed on the list as well, if dropdown is opened after a previous selection has been made:
Will it still work for you?

Instead of keeping the state of the selected element i would simply go over all options and add the space if that option is not selected:
function onDeviceSelection(event){
// Update textarea
output.val(output.val() + "\nonDeviceSelection");
// Higlight the selected
const {options, selectedIndex} = event.target;
for(let i = 0; i < options.length; i++)
options[i].innerHTML = (i === selectedIndex ? "":" ") + options[i].text.trim();
}
$("#select").on("change", onDeviceSelection);
Note that you need to use innerHTML to set the whitespace...

Get the values of all select options on change event javascript

I want to know all the values of a select element once the change event is recorded on it.
Code is like this:
PHP
<select name='variant' class='variantsselect' onchange='on(this.value)'>
<option value='a'>a</option>
<option value='a'>a</option>
</select>
JAVASCRIPT
function on(value){
alert(value); //This gives me selected value
};
I need values a & b when change event is recorded on select element. Can someone help?

<select name='variant' class='variantsselect' onchange="javascript:valueselect(this)">
function valueselect(sel) {
var value = sel.options[sel.selectedIndex].value;
alert(value)
}
EDIT:
<select name='variant' id='variant' class='variantsselect' onchange="javascript:displayResult()">
function displayResult() {
var x = document.getElementById("variant");
var i;
var txt = "Text: ";
for (i = 0; i < x.length; i++) {
txt = txt + "\n" + x.options[i].text;
}
alert(txt);
}

You can store the last selected value in a variable and overwrite the variable with the new selected value at the end of your function. When the function is called the variable will = to the last option selected (If you don't set a default value the variable will be empty on the first call)
Click Here For Demo
OR
This will work for a simple hide/show select without having to remember the previous selection.
The hide/show content have a class name of HideShow, this class name css display is set to none. When you change the option it will loop through all elements using the class name HideShow to compare the selected value with the id of the element, if they match it will set the style display to block }else{ set style display to none.
Demo
function HideShow(Selection){
var HScontent=document.getElementsByClassName('HideShow');
for(var i=0; i<HScontent.length; i++){
if(HScontent[i].id==Selection){
HScontent[i].style.display="block";
}else{
HScontent[i].style.display="none";
}
}
}
.HideShow{display:none;}
<select onchange="HideShow(this.value);">
<option value="cars">Cars</option>
<option value="bikes">Bikes</option>
<option value="buses">Buses</option>
</select>
<div id="cars" class="HideShow">Cars content.....</div>
<div id="bikes" class="HideShow">Bikes content....</div>
<div id="buses" class="HideShow">Buses content....</div>
If you don't understand something in the demo, leave a comment below and I will try get back to you as soon as possible.
I hope this helps. Happy coding!

<select> tag and returning multiple values to javascript method

I have an issue with the data which is sent from a drop down menu, the selector only returns a single value, even when multiple values are selected. I have searched online for a solution to this, but they all use PHP, JQuery or some method outside the scope of the course I am taking; to capture multiple selected items. I have tried .value of the individual options, but that returns all of the options rather than just the ones which are selected. Is there some kind of trick to sending multiple values?
Here is my code for the menu. For example If I select JAVA PROGRAMMING, NETWORKS and VIDEO GAMES, only JAVA PROGRAMMING is sent.
<select multiple id="CK_Expertise">
<option id="CK_Exp1" value="Java programming">JAVA PROGRAMMING</option>
<option id="CK_Exp2" value="Networks">NETWORKS</option>
<option id="CK_Exp3" value="Video game programming">VIDEO GAMES</option>
<option id="CK_Exp4" value="Accounter">ACCOUNTER</option>
<option id="CK_Exp5" value="Help Desk">HELPDESK</option>
<option id="CK_Exp6" value="C++ programming">C++</option>
<option id="CK_Exp7" value="Programming">PROGRAMMING</option>
</select>
I have also tried using the Select Object in the DOM, http://www.w3schools.com/jsref/dom_obj_select.asp
which has a few methods for accessing the options in the dropdown menu. One method in particular called selectedIndex, seemed to be what I am looking for, however it only returns the the index of the first selected option, instead of all of the selected options.
Is there a simple solution to this using just Javascript and the DOM?
Thanks
- Chris

Get the options, iterate and check if they are selected, and add the values to an array
var select = document.getElementById('CK_Expertise'),
options = select.getElementsByTagName('option'),
values = [];
for (var i=options.length; i--;) {
if (options[i].selected) values.push(options[i].value)
}
console.log(values)
FIDDLE
or being a little more fancy
var select = document.getElementById('CK_Expertise'),
values = Array.prototype.filter.call(select.options, function(el) {
return el.selected;
}).map(function(el) {
return el.value;
});
console.log(values)
FIDDLE

You could use the select.selectedOptions property:
select.onchange = function() {
var values = [].map.call(this.selectedOptions, function(opt){
return opt.value;
});
};
document.getElementById('CK_Expertise').onchange = function() {
document.querySelector('pre').textContent = JSON.stringify([].map.call(
this.selectedOptions, function(opt){ return opt.value; }
));
}
<select multiple id="CK_Expertise">
<option id="CK_Exp1" value="Java programming">JAVA PROGRAMMING</option>
<option id="CK_Exp2" value="Networks">NETWORKS</option>
<option id="CK_Exp3" value="Video game programming">VIDEO GAMES</option>
<option id="CK_Exp4" value="Accounter">ACCOUNTER</option>
<option id="CK_Exp5" value="Help Desk">HELPDESK</option>
<option id="CK_Exp6" value="C++ programming">C++</option>
<option id="CK_Exp7" value="Programming">PROGRAMMING</option>
</select>
<pre></pre>

If you can use jQuery, this will give you all the values
$(document).ready(function(){
$('#CK_Expertise').change(function(e){
var values = $('#CK_Expertise').val()
alert(values);
});
});
HTH,
-Ted

You could iterate storing select.selectedIndex in an array and unselecting the corresponding option to get the next one:
select.onchange = function() {
var i, indices=[], values = [];
while((i=this.selectedIndex) > -1) {
indices.push(i);
values.push(this.value);
this.options[i].selected = false;
}
while((i=indices.pop()) > -1)
this.options[i].selected = true;
console.log(values);
}
Demo
This way you avoid iterating over all options, but you must iterate twice over the selected ones (first to unselect them, them to select them again).

Why not using an indexed variable in the SELECT command?
<SELECT MULTIPLE id="stuff" name="stuff[]">
<OPTION value=1>First stuff</option>
<OPTION value=2>Second stuff</option>
<OPTION value=3>Third stuff</option>
</SELECT>
In that case it's easy to read the array:
$out=$_REQUEST['stuff'];
foreach($out AS $thing) {
echo '<br />'.$thing;
}
Sorry for the poor indentation, but I just wanted to show the way I use for solving this case!

var select = document.getElementById('CK_Expertise'),
options = select.selectedOptions,
values = [];
for(let i=0;i<options.length;i++)
{
values.push(options[i].value);
}
console.log(values);

Set HTML attribute value using java Script

I have html drop down list,which has country list. Now I want to set current country as a default value of list. I found the JavaScript code for get country using Geolocation.
My code:
function getCountry(var name) {
if(name==geoip_country_name()) {
return "selected";
}
}
Then I need to set the selected attribute of the option list.
I tried this:
<option value="Sri Lanka" selected="getCountry('sri Lanka')">Sri Lanka</option>
But this is not correct.
Basically I want to set selected attribute value using JavaScript function
How do I do that?

Use the window.onload event, and just set the dropdown's value. Keep in mind that your hard coded country names may differ from the geo service.
<script>
window.onload = function(){
document.getElementById("country").value = geoip_country_name();
}
</script>
<select id="country" name="country">
<option value="Sri Lanka">Sri Lanka</option>
<option value="UK">UK</option>
<option value="USA">USA</option>
<select>

Basically you can do it like this:
<html>
<body>
<select id="country">
<option id="germany" value="Germany">DE</option>
<option id="uk" value="UK">UK</option>
<option id="usa" value="USA">USA</option>
</select>
<script>
var selectedCountry = 'uk'; //getCountry
var index = document.getElementById(selectedCountry).index;
document.getElementById("country").selectedIndex=index;
</script>
Start the script after your select is rendered.
Note, that this example might not be best practice. I'm also not sure if it works in all browsers (Opera works). You might use an appropriate framework like JQuery, Mootools, ...

The selected attribute is not automatically evaluated as JS code. Assuming you have stored the desired country name in the variable country, could try this instead:
var country = "Sri Lanka";
var select = document.getElementById('myselect'); //Change to the ID of your select element
for (var i = 0; i < select.options.length; i++){
if(select.options[i].value == country)
select.selectedIndex = i;
}

If you are using JQuery following line should solve your problem:
$('select').val(geoip_country_name());
If geoip_country_name returns names in lower case, While initializing the select list, value for each option be in lower case.

Javascript to hide select box elements not working in IE

Hey, not sure if I'm going about this the right way. I have two different select boxed. What needs to happen is when a certain item in box 1 is selected, certain items in box 2 are hidden. What I have works fine in FF but not in IE....thoughts?
<div>
<label class="form_label">Apparel</label>
<select id="Choices" size="1" style="clear: right;" onchange"changeThis();">
<option value="select">Pick Your Product</option>
<option value="1">choice 1</option>
<option value="2">choice 2/option>
<option value="3">choice 3</option>
</select>
</div>
<div>
<label class="form_label">Size</label>
<select id="Sizes" size="1" style="clear: right;">
<option value="select">Choose Your Size</option>
<option value="SC">Small Child</option>
<option value="IC">Intermediate Child</option>
<option value="MC">Medium Child</option>
</select>
</div>
...
function changeThing(choice)
{
var item = document.getElementById("Choices");
var size = document.getElementById("Sizes");
var selitem = item.options[item.selectedIndex].value;
if(selitem == '2546')
{
for(i=0; i<2; i++)
{
size[i].style.display = 'none';
//alert(size[i]);
}
}

Try using this instead:
http://www.w3schools.com/CSS/pr_class_visibility.asp
It would come out as:
size[i].style.visibility='hidden';
EDIT
Oh, welcome to StackOverflow!

I had the same problem some days ago. IE does not allow the using of visible:hidden or display:none for option element.
You can solve this problem storing the options of select1 in a variable. This variable will have all possible values, so when the value of select1 was changed you can remove all values of select2 and then get the options you need from variable to put into select2.
To summarize:
Store all possible values in a variable
When select1 was changed remove all options of select2
Filter the options(get these values from varible of step1) you need and put into select2

You cannot display:none remove will completely remove it, if you want the user not to choose it use disabled. you could do something like this
function changeThing()
{
var item = document.getElementById("Choices");
var size = document.getElementById("Sizes");
var selitem = item.options[item.selectedIndex].value;
if(selitem == '3')
{
for(i=1; i<2; i++) // filter logic here
{
size[i].disabled = true; //false - to reset
//alert(size[i]);
}
}
size.selectedIndex = 0; // reset the selection so a disabled item may not be selected. }

It depends on how you are firing off the event that calls the changeThing() function. Not sure about IE9, but IE8 and on back has issues with the onChange event. It basically avoids it in IE. You'll have to use onClick instead.
If you are using jQuery to fire the event, the onchange event should work correctly in all browser (even IE). Not sure how other Javascript libraries do it.

You need to remove this options completely to make it work in IE.
size.remove(i);
So you need to store your options in array and load it back when needed.