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Is it possible to trigger JavaScript when a user selects the current option in an HTML select?

I know that you can use the onchange event on the select to trigger a JavaScript function, but what if they choose the option that is currently selected?
The reason for this is I want to have a drop down list of a bunch of websites. This is used as a sort of jumppage, if you will. When the user selects a site the selected site opens in a new window. Now if they close the new tab/window the select is on the last option they selected. If the user wants to go to the same website again the onchange event does not fire.
I know that you can change the select option back to the default option with a null value like this:
html
<select onChange="jsFunction(this.value)" id="selectOpt">
<option value="">1</option>
<option value="websiteURL2">2</option>
<option value="websiteURL3">3</option>
</select>
javascript
function jsFunction(opt){
window.location = opt;
document.getElementById("selectOpt").options[0].selected = true;
}
http://jsfiddle.net/XqLmY/1/
But I was wondering if it could be done without that.
Can I trigger an event using a HTML select without changing its value?

What about using onClick instead
Look here http://jsfiddle.net/9X4Ks/1/
<select onclick="clickFunction(this)" id="selectOpt">
<option value="websiteURL1">1</option>
<option value="websiteURL2">2</option>
<option value="websiteURL3">3</option>
</select>
function clickFunction(o){
alert(o.value)
}
It fires even when user clicks the selected option second time.
Unfortunately it works only in chrome and opera.
Does not work in firefox

Not really an answer, but I just ended up using this method because it was easy and didn't have other dependencies.
function jsFunction(opt){
window.location = opt;
document.getElementById("selectOpt").options[0].selected = true;
}

Clicking drop down with Selenium WebDriver does not activate Javascript to add or remove items from the page.

When I click an item in a drop down it doesn't activate the javascript on a given page.
Here is the element I am interacting with
<select id="DocumentComment_document_id" name="DocumentComment[document_id]">
<option value=""></option>
<option value="1">Document 1</option>
<option value="2">Document 2</option>
</select>
Here is the Javascript that actually does the work
jQuery(function($) {
$("#DocumentComment_document_id").live("change", function(){
$.post(
"/wg/wg2/documentComment/ajaxLoadDelineators",
{"docID": $(this).val(),"ajax":true},
function(data){
$("#delineator_options").html(data);
}
);
return false;
});

Your question isn't very clear but you can define a "mouse action" with the Action class that will physically move the point pointer and click. I would bet that would work where it wasn't working using the JavascriptExecutor.
Really, I don't see how you could go wrong here because you seem to see the entire option element contents which means that WebDriver should have no problem getting one of the 2 option elements and clicking it the standard way.

A browser independent way to select an option from a traditional dropdown is just to click the option, without clicking the select first. It goes against the norm for Selenium, but it works
C# code (to select Document 1):
IWebElement theOption = _webDriver.FindElement(By.XPath("//select[#id='DocumentComment_document_id']/option[#value='1']"));
theOption.Click();

How to reselect already selected option

The title seems confusing but what I want to do is...
I know how to handle only if the user select new option with this - $('select').change(function(){}).`
But not if the user wants to select the already selected option.
I've also tried with radio but same thing.
Okay for example I have a select with an option (red,blue,green).
<select>
<option value="red">RED</option>
<option value="blue">BLUE</option>
<option value="green">GREEN</option>
</select>
and I have this script:
$('select').change(function(){
var val = $(this).val();
alert(val);
});
When I select option 'blue' it alerts a value 'blue', then I select 'green' it alerts 'green' as well. but when I select 'green' again nothing happens.

This question comes to my attention as this is pretty basic stuff but no one actually dig into it further. OP has been using change(), but when you reselect the current selected option nothing is fired!
I tried click(), but it's firing before you can even choose an option.
With blur(), after you're done selecting nothing is fired because the the select element is still being focused, so you need to focus out like clicking outside for it to execute.
So I just suggested OP to switch to a radio type input then handle execution with click() event. That way you can still reselect already marked radio button.
But then I noticed that you just need to get the second click on <select> element because the first click opens the drop down list of options the second click returns the value of your selected option. So I came up with this:
$('select').click(function(){
var $this = $(this);
if ($this.hasClass('open')) {
alert($this.val());
$this.removeClass('open');
}else {
$this.addClass('open');
}
});
But now the problem is when you first click on <select> the drop down is being showned and we've also added the class 'open'. Then clicking elsewhere (without selecting an option) the drop down is hidden so when you click back on <select> the event is fired before you can even select an option.
So I added this code to fix that:
$(document).click(function(e){
var $select = $('select');
if (!$select.is(e.target)){
$select.removeClass('open'); //reset the steps by removing open
}
});
You can test it out in this jsfiddle. Cheers!
I think when <select> loses its focus is also a concern. So I added blur() event. See this update jsfiddle

i solved using onclick='this.value=-1' that reset the selection to nothing...

I have solved this problem by using:
$('#id_selec').on('click', 'option', function (e) {
value = $(this).val();
// ....
The handler works if you select any (including the already selected) option.

In instances where nothing should happen when the user selects the already-selected option I suppose it is a "feature" of the DOM rather than a bug to have no Event occur. However, if your code is doing more with <select> than making a simple selection it is also a nuisance, so I'm grateful others have tackled it here.
The current accepted answer is clever in the use of the click event to capture selection of an already selected <select> option, but if you are willing to specify the length of your list as (in this case) <select size=3>, you can simply set the selected value to "" from your "change" Event, and the same selection will trigger every time.
In this case the OP's example would change to:
HTML:
<select size=3>
<option value="red">RED</option>
<option value="blue">BLUE</option>
<option value="green">GREEN</option>
</select>
jQuery:
$('select').change(function(){
var val = $(this).val();
alert(val);
$('select').val("");
});
The only side-effect is that the selection element may now display to the user as three rows rather than one.
(Credit goes to Kirby L. Wallace for the idea of setting the select's value to "").

How to make the "change event" work on a select drop-down menu when using .attr()

I have the select drop-down menu below:
<select id="select-param-num">
<option value='0'>0</option>
<option value='1'>1</option>
<option value='2'>2</option>
</select>
I have the trigger bellow, to update things on my page when the user change the selected option: (I am calling that first)
$('#select-param-num').change(function () {
//update stuff
});
And then in my initialization I am setting the drop-down menu at a specific value like this:
$("select#select-param-num option[value=2]").attr('selected', true);
I was expecting that .change() would have been called, to automatically update my page but it doesn't.
Do you have any suggestion to make it happen?
Thanks

Just trigger the event, 3 ways for that:
$('#select-param-num').change(); //same as .trigger('change')
$('#select-param-num').trigger('change'); //same as .change()
$('#select-param-num').triggerHandler('change'); //same as others but just because change event doesn't bubble

Use .triggerHandler to run your event handling code:
$("#select-param-num").triggerHandler('change');
You should also not use .attr to set the value of the dropdown. Do this instead:
$("#select-param-num").val("2");

You can use trigger for that .
$('#select-param-num').trigger('change');
.trigger()

In your select, there's no option with value=6. If you add it, and change a little the code, it works. Have a look here: http://jsfiddle.net/sjJkN/
code
$('#select-param-num').change(function () {
$("select#select-param-num option[value=6]").attr('selected', 'selected');
});

Is there an onSelect event or equivalent for HTML <select>?

I have an input form that lets me select from multiple options, and do something when the user changes the selection. Eg,
<select onChange="javascript:doSomething();">
<option>A</option>
<option>B</option>
<option>C</option>
</select>
Now, doSomething() only gets triggered when the selection changes.
I want to trigger doSomething() when the user selects any option, possibly the same one again.
I have tried using an "onClick" handler, but that gets triggered before the user starts the selection process.
So, is there a way to trigger a function on every select by the user?
Update:
The answer suggested by Darryl seemed to work, but it doesn't work consistently. Sometimes the event gets triggered as soon as user clicks the drop-down menu, even before the user has finished the selection process!

I needed something exactly the same. This is what worked for me:
<select onchange="doSomething();" onfocus="this.selectedIndex = -1;">
<option>A</option>
<option>B</option>
<option>C</option>
</select>
Supports this:
when the user selects any option, possibly the same one again

Here is the simplest way:
<select name="ab" onchange="if (this.selectedIndex) doSomething();">
<option value="-1">--</option>
<option value="1">option 1</option>
<option value="2">option 2</option>
<option value="3">option 3</option>
</select>
Works both with mouse selection and keyboard Up/Down keys whes select is focused.

I had the same problem when I was creating a design a few months back. The solution I found was to use .live("change", function()) in combination with .blur() on the element you are using.
If you wish to have it do something when the user simply clicks, instead of changing, just replace change with click.
I assigned my dropdown an ID, selected, and used the following:
$(function () {
$("#selected").live("change", function () {
// do whatever you need to do
// you want the element to lose focus immediately
// this is key to get this working.
$('#selected').blur();
});
});
I saw this one didn't have a selected answer, so I figured I'd give my input. This worked excellently for me, so hopefully someone else can use this code when they get stuck.
http://api.jquery.com/live/
Edit: Use the on selector as opposed to .live. See jQuery .on()

Just an idea, but is it possible to put an onclick on each of the <option> elements?
<select>
<option onclick="doSomething(this);">A</option>
<option onclick="doSomething(this);">B</option>
<option onclick="doSomething(this);">C</option>
</select>
Another option could be to use onblur on the select. This will fire anytime the user clicks away from the select. At this point you could determine what option was selected. To have this even trigger at the correct time, the onclick of the option's could blur the field (make something else active or just .blur() in jQuery).

If you really need this to work like this, I would do this (to ensure it works by keyboard and mouse)
Add an onfocus event handler to the select to set the "current" value
Add an onclick event handler to the select to handle mouse changes
Add an onkeypress event handler to the select to handle keyboard changes
Unfortunately the onclick will run multiple times (e.g. on onpening the select... and on selection/close) and the onkeypress may fire when nothing changes...
<script>
function setInitial(obj){
obj._initValue = obj.value;
}
function doSomething(obj){
//if you want to verify a change took place...
if(obj._initValue == obj.value){
//do nothing, no actual change occurred...
//or in your case if you want to make a minor update
doMinorUpdate();
} else {
//change happened
getNewData(obj.value);
}
}
</script>
<select onfocus="setInitial(this);" onclick="doSomething();" onkeypress="doSomething();">
...
</select>

The onclick approach is not entirely bad but as said, it will not be triggered when the value isn't changed by a mouse-click.
It is however possible to trigger the onclick event in the onchange event.
<select onchange="{doSomething(...);if(this.options[this.selectedIndex].onclick != null){this.options[this.selectedIndex].onclick(this);}}">
<option onclick="doSomethingElse(...);" value="A">A</option>
<option onclick="doSomethingElse(..);" value="B">B</option>
<option onclick="doSomethingElse(..);" value="Foo">C</option>
</select>

I know this question is very old now, but for anyone still running into this problem, I have achieved this with my own website by adding an onInput event to my option tag, then in that called function, retrieving the value of that option input.
<select id='dropdown' onInput='myFunction()'>
<option value='1'>1</option>
<option value='2'>2</option>
</select>
<p>Output: </p>
<span id='output'></span>
<script type='text/javascript'>
function myFunction() {
var optionValue = document.getElementById("dropdown").value;
document.getElementById("output").innerHTML = optionValue;
}
</script>

Going to expand on jitbit's answer. I found it weird when you clicked the drop down and then clicked off the drop down without selecting anything. Ended up with something along the lines of:
var lastSelectedOption = null;
DDChange = function(Dd) {
//Blur after change so that clicking again without
//losing focus re-triggers onfocus.
Dd.blur();
//The rest is whatever you want in the change.
var tcs = $("span.on_change_times");
tcs.html(+tcs.html() + 1);
$("span.selected_index").html(Dd.prop("selectedIndex"));
return false;
};
DDFocus = function(Dd) {
lastSelectedOption = Dd.prop("selectedIndex");
Dd.prop("selectedIndex", -1);
$("span.selected_index").html(Dd.prop("selectedIndex"));
return false;
};
//On blur, set it back to the value before they clicked
//away without selecting an option.
//
//This is what is typically weird for the user since they
//might click on the dropdown to look at other options,
//realize they didn't what to change anything, and
//click off the dropdown.
DDBlur = function(Dd) {
if (Dd.prop("selectedIndex") === -1)
Dd.prop("selectedIndex", lastSelectedOption);
$("span.selected_index").html(Dd.prop("selectedIndex"));
return false;
};
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<select id="Dd" onchange="DDChange($(this));" onfocus="DDFocus($(this));" onblur="DDBlur($(this));">
<option>1</option>
<option>2</option>
</select>
<br/>
<br/>Selected index: <span class="selected_index"></span>
<br/>Times onchange triggered: <span class="on_change_times">0</span>
This makes a little more sense for the user and allows JavaScript to run every time they select any option including an earlier option.
The downside to this approach is that it breaks the ability to tab onto a drop down and use the arrow keys to select the value. This was acceptable for me since all the users click everything all the time until the end of eternity.

To properly fire an event every time the user selects something(even the same option), you just need to trick the select box.
Like others have said, specify a negative selectedIndex on focus to force the change event. While this does allow you to trick the select box, it won't work after that as long as it still has focus. The simple fix is to force the select box to blur, shown below.
Standard JS/HTML:
<select onchange="myCallback();" onfocus="this.selectedIndex=-1;this.blur();">
<option>A</option>
<option>B</option>
<option>C</option>
</select>
jQuery Plugin:
<select>
<option>A</option>
<option>B</option>
<option>C</option>
</select>
<script type="text/javascript">
$.fn.alwaysChange = function(callback) {
return this.each(function(){
var elem = this;
var $this = $(this);
$this.change(function(){
if(callback) callback($this.val());
}).focus(function(){
elem.selectedIndex = -1;
elem.blur();
});
});
}
$('select').alwaysChange(function(val){
// Optional change event callback,
// shorthand for $('select').alwaysChange().change(function(){});
});
</script>
You can see a working demo here.

first of all u use onChange as an event handler and then use flag variable to make it do the function u want every time u make a change
<select
var list = document.getElementById("list");
var flag = true ;
list.onchange = function () {
if(flag){
document.bgColor ="red";
flag = false;
}else{
document.bgColor ="green";
flag = true;
}
}
<select id="list">
<option>op1</option>
<option>op2</option>
<option>op3</option>
</select>

This may not directly answer your question, but this problem could be solved by simple design level adjustments. I understand this may not be 100% applicable to all use-cases, but I strongly urge you to consider re-thinking your user flow of your application and if the following design suggestion can be implemented.
I decided to do something simple than hacking alternatives for onChange() using other events that were not really meant for this purpose (blur, click, etc.)
The way I solved it:
Simply pre-pend a placeholder option tag such as select that has no value to it.
So, instead of just using the following structure, which requires hack-y alternatives:
<select>
<option>A</option>
<option>B</option>
<option>C</option>
</select>
Consider using this:
<select>
<option selected="selected">Select...</option>
<option>A</option>
<option>B</option>
<option>C</option>
</select>
So, this way, your code is a LOT more simplified and the onChange will work as expected, every time the user decides to select something other than the default value. You could even add the disabled attribute to the first option if you don't want them to select it again and force them to select something from the options, thus triggering an onChange() fire.
At the time of this answer, I'm writing a complex Vue application and I found that this design choice has simplified my code a lot. I spent hours on this problem before I settled down with this solution and I didn't have to re-write a lot of my code. However, if I went with the hacky alternatives, I would have needed to account for the edge cases, to prevent double firing of ajax requests, etc. This also doesn't mess up the default browser behaviour as a nice bonus (tested on mobile browsers as well).
Sometimes, you just need to take a step back and think about the big picture for the simplest solution.

Add an extra option as the first, like the header of a column, which will be the default value of the dropdown button before click it and reset at the end of doSomething(), so when choose A/B/C, the onchange event always trigs, when the selection is State, do nothing and return. onclick is very unstable as many people mentioned before. So all we need to do is to make an initial button label which is different as your true options so the onchange will work on any option.
<select id="btnState" onchange="doSomething(this)">
<option value="State" selected="selected">State</option>
<option value="A">A</option>
<option value="B">B</option>
<option value="C">C</option>
</select>
function doSomething(obj)
{
var btnValue = obj.options[obj.selectedIndex].value;
if (btnValue == "State")
{
//do nothing
return;
}
// Do your thing here
// reset
obj.selectedIndex = 0;
}

Actually, the onclick events will NOT fire when the user uses the keyboard to change the selection in the select control. You might have to use a combination of onChange and onClick to get the behavior you're looking for.

The wonderful thing about the select tag (in this scenario) is that it will grab its value from the option tags.
Try:
<select onChange="javascript:doSomething(this.value);">
<option value="A">A</option>
<option value="B">B</option>
<option value="Foo">C</option>
</select>
Worked decent for me.

2022 VANILLA JAVASCRIPT
...because this is a top hit on Google.
Original Poster did NOT ask for a JQuery solution, yet all answers ONLY demonstrate JQuery or inline SELECT tag event.
Use an event listener with the 'change' event.
const selectDropdown = document.querySelector('select');
selectDropdown.addEventListener('change', function (e) { /* your code */ });
... or call a seperate function:
function yourFunc(e) { /* your code here */ }
const selectDropdown = document.querySelector('select');
selectDropdown.addEventListener('change', yourFunc);

What I did when faced with a similar Problem is I added an 'onFocus' to the select box which appends a new generic option ('select an option'or something similar) and default it as the selected option.

So my goal was to be able to select the same value multiple times which essentially overwrites the the onchange() function and turn it into a useful onclick() method.
Based on the suggestions above I came up with this which works for me.
<select name="ab" id="hi" onchange="if (typeof(this.selectedIndex) != undefined) {alert($('#hi').val()); this.blur();}" onfocus="this.selectedIndex = -1;">
<option value="-1">--</option>
<option value="1">option 1</option>
<option value="2">option 2</option>
<option value="3">option 3</option>
</select>
http://jsfiddle.net/dR9tH/19/

Kindly note that Event Handlers are not supported for the OPTION tag on IE, with a quick thinking..I came up with this solution, try it and give me your feedback:
<script>
var flag = true;
function resetIndex(selObj) {
if(flag) selObj.selectedIndex = -1;
flag = true;
}
function doSomething(selObj) {
alert(selObj.value)
flag = false;
}
</script>
<select onchange="doSomething(this)" onclick="resetIndex(this)">
<option value="A">A</option>
<option value="B">B</option>
<option value="C">C</option>
</select>
What I'm doing here actually is resetting the select index so that the onchange event will be triggered always, true that you we lose the selected item when you click and it maybe annoying if your list is long, but it may help you in someway..

use jquery:
<select class="target">
<option>A</option>
<option>B</option>
<option>C</option>
</select>
<script>
$('.target').change(function() { doSomething(); });
</script>

Here's my solution, completely different to any else on here. It uses the mouse position to figure out if an option was clicked as oppose to clicking on the select box to open the dropdown. It makes use of the event.screenY position as this is the only reliable cross browser variable. A hover event has to be attached first so it can figure out the controls position relative to the screen before the click event.
var select = $("select");
var screenDif = 0;
select.bind("hover", function (e) {
screenDif = e.screenY - e.clientY;
});
select.bind("click", function (e) {
var element = $(e.target);
var eventHorizon = screenDif + element.offset().top + element.height() - $(window).scrollTop();
if (e.screenY > eventHorizon)
alert("option clicked");
});
Here is my jsFiddle
http://jsfiddle.net/sU7EV/4/

you should try using option:selected
$("select option:selected").click(doSomething);

What works for me:
<select id='myID' onchange='doSomething();'>
<option value='0' selected> Select Option </option>
<option value='1' onclick='if (!document.getElementById("myID").onchange()) doSomething();' > A </option>
<option value='2' onclick='if (!document.getElementById("myID").onchange()) doSomething();' > B </option>
</select>
In that way, onchange calls 'doSomething()' when the option changes, and
onclick calls 'doSomething()' when onchange event is false, in other words, when you select the same option

Try this (event triggered exactly when you select option, without option changing):
$("select").mouseup(function() {
var open = $(this).data("isopen");
if(open) {
alert('selected');
}
$(this).data("isopen", !open);
});
http://jsbin.com/dowoloka/4

The one True answer is to not use the select field (if you need to do something when you re-select same answer.)
Create a dropdown menu with conventional div, button, show/hide menu. Link: https://www.w3schools.com/howto/howto_js_dropdown.asp
Could have been avoided had one been able to add event listeners to options. If there had been an onSelect listener for select element. And if clicking on the select field didn't aggravatingly fire off mousedown, mouseup, and click all at the same time on mousedown.

<script>
function abc(selectedguy) {
alert(selectedguy);
}
</script>
<select onchange="abc(this.selectedIndex);">
<option>option one</option>
<option>option two</option>
</select>
Here you have the index returned, and in the js code you can use this return with one switch or anything you want.

Try this:
<select id="nameSelect" onfocus="javascript:document.getElementById('nameSelect').selectedIndex=-1;" onchange="doSomething(this);">
<option value="A">A</option>
<option value="B">B</option>
<option value="C">C</option>
</select>

A long while ago now but in reply to the original question, would this help ?
Just put onClick into the SELECT line.
Then put what you want each OPTION to do in the OPTION lines.
ie:
<SELECT name="your name" onClick>
<option value ="Kilometres" onClick="YourFunction()">Kilometres
-------
-------
</SELECT>

<select name="test[]"
onchange="if(this.selectedIndex < 1){this.options[this.selectedIndex].selected = !1}">
<option>1</option>
<option>2</option>
<option>3</option>
</select>

I had faced a similar need and ended up writing a angularjs directive for the same -
guthub link - angular select
Used element[0].blur(); to remove the focus off the select tag. Logic is to trigger this blur on second click of the dropdown.
as-select gets triggered even when user selects the same value in the dropdown.
DEMO - link

There are a few things you want to do here to make sure it remembers older values and triggers an onchange event even if the same option is selected again.
The first thing you want is a regular onChange event:
$("#selectbox").on("change", function(){
console.log($(this).val());
doSomething();
});
To have the onChange event trigger even when the same option is selected again, you can unset selected option when the dropdown receives focus by setting it to an invalid value. But you also want to store the previously selected value to restore it in case the user does not select any new option:
prev_select_option = ""; //some kind of global var
$("#selectbox").on("focus", function(){
prev_select_option = $(this).val(); //store currently selected value
$(this).val("unknown"); //set to an invalid value
});
The above code will allow you to trigger onchange even if the same value is selected. However, if the user clicks outside the select box, you want to restore the previous value. We do it on onBlur:
$("#selectbox").on("blur", function(){
if ($(this).val() == null) {
//because we previously set an invalid value
//and user did not select any option
$(this).val(prev_select_option);
}
});