Develop Reference

How to use getElementByID in JavaScript to connect to my HTML drop down box?

I have a drop-down box in HTML showing three options. I am also using javaScript and want to use the getElementById tool to connect the two. However, I only have one ID for the drop-down box. How does javascript recognize that I have three different options?

There's actually a demo on w3schools.com showing exactly what you're asking. To get the number of options, you could do something like
document.getElementById("mySelect").options.length

Here is an example of how to retrieve the value of a dropdown: https://jsfiddle.net/ykcwgnm8/
You use getElementBy* functions to get the element, however value attribute denotes which item is currently selected.
HTML:
<select id="dropdown">
<option value="1">First option</option>
<option value="2">Second option</option>
<option value="3">Third option</option>
</select>
JS:
function onChangeHandler(e)
{
alert("you have selected item with value "+this.value);
}
document.getElementById("dropdown").addEventListener("change", onChangeHandler);

You can listen for change like this
var list = document.getElementById("mySelect")
list.addEventListener('change', function(e){
console.log(e.target.selectedIndex)
console.log(e.target.options[e.target.selectedIndex].text)
})
<select id="mySelect">
<option>Apple</option>
<option>Orange</option>
<option>Pineapple</option>
<option>Banana</option>
</select>

You can do something like this, here is an example:-
html
<select id="selectBox">
<option value="1">option 1</option>
<option value="2" selected="selected">option 2</option>
<option value="3">option 3</option>
</select>
js
var e = document.getElementById("selectBox");
var selectedValue = e.options[e.selectedIndex].value;
// this will give selectedValue as 2
Hope you find this useful!!

I have two select boxes. I want to enable second select box only if i click a particular option in first select box [duplicate]

I have two dynamic dropdowns but both dropdown's value and options are same. What I want that if user select 'apple' from first dropdown then the second dropdown's apple option will be disabled (using javascript). In short user can not select same value from both.
//first drop down
<select name="fruit1">
<option value="1">Apple</option>
<option value="2">Mango</option>
</select>
//second dropdown
<select name="fruit2">
<option value="1">Apple</option>
<option value="2">Mango</option>
</select>
I have tried with jQuery:
function witness()
{
var op=document.getElementById("witness1").value;
$('option[value='+op+']').prop('disabled', true);
}
But with this both dropdown's value are disabled and if I select mango then apple will not enabled it remains disabled. I know I did not pass id so both dropdown value are disabled but where should i pass ?
If user select apple then in second dropdown apple will be disabled, I want to do this using Javascript or jQuery.

Fiddle: https://jsfiddle.net/3pfo1d1f/
To get the functionality you're after, you need to hook into the change event on the first dropdown, in order to disable the matching element in the second drop-down.
I also initialised the first element in the second dropdown as disabled ( as this chosen by default in the first dropdown)
Used jquery as you are:
HTML:
<!-- first dropdown -->
<select id="fruit1">
<option value="1">Apple</option>
<option value="2">Mango</option>
</select>
<br /> <br />
<!-- second dropdown -->
<select id="fruit2">
<option value="1" disabled>Apple</option>
<option value="2">Mango</option>
</select>
JQuery:
$('#fruit1').on( "change", function() {
var op = $( this ).val();
$('#fruit2 option').prop('disabled', false);
$('#fruit2 option[value='+op+']').prop('disabled', true);
});
This should still work, no matter how many options you have in both the dropdowns

Try this out:
HTML:
<select id='fruit1' onchange="witness();">
<option selected></option>
<option value="1">Apple</option>
<option value="2">Mango</option>
</select>
<select id='fruit2'>
<option selected></option>
<option value="1">Apple</option>
<option value="2">Mango</option>
</select>
JQuery:
function witness(){
$("#fruit2 option").each(function(){
if($("#fruit1 option:selected").val() == $(this).val())
$(this).attr("disabled", "disabled");
else
$(this).removeAttr("disabled");
});
}
You can see a working exemple here:
https://jsfiddle.net/mqjxL4n0/

<select name="firstselect" id="firstselect">
<option value="apple">Apple</option>
<option value="orange">Orange</option>
</select>
<select name="secondselect" id="secondselect">
<option value="apple">Apple</option>
<option value="orange">Orange</option>
</select>
<script>
$(document).ready(function(){
$('#firstselect').change(function(){
var firstselected = $(this).val();
if(firstselected ){
$('#secondselect option').each(function(){
$(this).prop('disabled', false);
if($(this).val()==firstselected )
$(this).prop('disabled', true);
});
}
else {
$('#secondselect option').each(function(){
$(this).prop('disabled', false);
});
}
});
});
</script>

Select Option dropdown taking time to close specifically in Chrome

I have two select option buttons on single web page but on different tabs. I want to change the other one button value on change of any one button and assign it to some element like span in example code. All things are working perfectly but it just taking time to close dropdown when i am changing value. in firefox there is no problem
jsfiddle
My HTML Code
<select class="select one" >
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
</select><br><br><br>
<select class="select two">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
</select>
<br><br><br>
<span class="value"></span>
JQuery
var lang = $('select.one').val();
$('span.value').text(lang);
$('select.select').change(function(){
lang = $(this).val();
$('span.value').text(lang);
if ($(this).hasClass('one')) {
$('.two').val($(this).val()).trigger('change');
}
else{
$('.one').val($(this).val()).trigger('change');
}
});
Thanks in advance

fixed jsFiddle demo
It's cause you're concurrently triggering changes. Cool that down, this is all you need:
var lang = $('select.one').val();
$('span.value').text(lang);
$('select.select').change(function () {
lang = this.value;
$('span.value').text(lang);
$('.select').val(lang);
});

You can try this instead:
var lang = $('.select.one').val();
$('.value').text(lang);
$('.select').change(function (e) {
$('.select').val(this.value);
$('.value').text(this.value);
});
The issue was .trigger() method, that was traversing up to the dom for lookup and setting the values to each elem again and again.
Check the updated fiddle.

Remove option in select

<select class="one">
<option></option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
</select>
<br />
<select class="one">
<option></option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
</select>
<br />
<select class="one">
<option></option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
</select>
$(".one").change(function(){
})
I would like make - for example if i select in first position option 1 then i others selects this option should be removed.
So if i in first select i select 1 then in select second and third i have only option 2 and 3. If in second select i select 2 then in last select i have only option 3.
How can i make it? I would like use jQuery.
LIVE: http://jsfiddle.net/9N9Tz/1/

If you need to sort something, consider using something like jQuery UI sortable as a bunch of drop down menus make a really poor UX for that.
But to answer your question:
var $selects = $('.one');
$selects.on("keyup click change", function(e) {
$selects.not(this).trigger('updateselection');
}).on("updateselection", function(e, data) {
var $this = $(this);
$this.children().show();
$selects.not(this).each(function() {
var value = $(this).val();
if (value) {
$this.children('[value="' + value + '"]').hide();
}
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<select class="one">
<option></option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
</select>
<br />
<select class="one">
<option></option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
</select>
<br />
<select class="one">
<option></option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
</select>
Hiding an option works in current firefox. I'm not sure about legacy browser. Hiding, but not removing, the element makes sure that you can change your selection without having crippled your input elements.

Here you go http://jsfiddle.net/Calou/9N9Tz/6/.
When the value of the <select>s changes, just take this value and search for the <option>s with this value in the others <select>s and remove them.
$(".one").change(function(){
var val = this.value
if (val !== '') {
$(this).siblings().find('option[value=' + val + ']').remove()
}
})

// As soon as all selects have one class, you'll have to distinguish them:
$(".one").each(function() {
// Now this corresponds to one select (in the loop over all)
$(this).change(function() {
// Fix what've done before
$('option').show();
// Find every other select, find an option in it
// that has the same value that is selected in current select
// (sorry for the description)
$('.one').not(this).find('option[value=' + $(this).find('option:selected').val() +']').hide();
});
})​;​
jsFiddle

It will be easy if you use different class for second and third select element
$(".one").change(function(){
var val = parseInt($(this).val());
$('.two,.three').find('option:contains('+val+')').remove();
});
EDIT:
Updated code to apply for multiple selects. [Thanks to all commentators and Alex for bringing it to notice ]
$(".one").change(function(){
var val = parseInt($(this).val());
$(this).siblings().find('option:contains('+val+')').remove();
});

JQuery - how to select dropdown item based on value

I want set a dropdown(select) to be change based on the value of the entries.
I have
<select id="mySelect">
<option value="ps">Please Select</option>
<option value="ab">Fred</option>
<option value="fg">George</option>
<option value="ac">Dave</option>
</select>
And I know that I want to change the dropdown so that the option with the value of "fg" is selected. How can I do this with JQuery?

You should use
$('#dropdownid').val('selectedvalue');
Here's an example:
$('#dropdownid').val('selectedvalue');
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<select id='dropdownid'>
<option value=''>- Please choose -</option>
<option value='1'>1</option>
<option value='2'>2</option>
<option value='selectedvalue'>There we go!</option>
<option value='3'>3</option>
<option value='4'>4</option>
<option value='5'>5</option>
</select>

$('#yourdropddownid').val('fg');
Optionally,
$('select>option:eq(3)').attr('selected', true);
where 3 is the index of the option you want.
Live Demo

$('#mySelect').val('fg');...........

$('#mySelect').val('ab').change();
// or
$('#mySelect').val('ab').trigger("change");

You can use this jQuery code which I find it eaiser to use:
$('#your_id [value=3]').attr('selected', 'true');
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<select id="your_id" name="name" class="form-control input-md">
<option value="1">Option #1</option>
<option value="2">Option #2</option>
<option value="3">Option #3</option>
<option value="4">Option #4</option>
<option value="5">Option #5</option>
<option value="6">Option #6</option>
<option value="7">Option #7</option>
</select>

You can simply use:
$('#select_id').val('fg')

In your case $("#mySelect").val("fg") :)

May be too late to answer, but at least some one will get help.
You can try two options:
This is the result when you want to assign based on index value, where '0' is Index.
$('#mySelect').prop('selectedIndex', 0);
don't use 'attr' since it is deprecated with latest jquery.
When you want to select based on option value then choose this :
$('#mySelect').val('fg');
where 'fg' is the option value

$('#dropdownid').val('selectedvalue');
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<select id='dropdownid'>
<option value=''>- Please choose -</option>
<option value='1'>1</option>
<option value='2'>2</option>
<option value='selectedvalue'>There we go!</option>
<option value='3'>3</option>
<option value='4'>4</option>
<option value='5'>5</option>
</select>

This code worked for me:
$(function() {
$('[id=mycolors] option').filter(function() {
return ($(this).text() == 'Green'); //To select Green
}).prop('selected', true);
});
With this HTML select list:
<select id="mycolors">
<option value="1">Red</option>
<option value="2">Green</option>
<option value="3">Blue</option>
</select>

I have a different situation, where the drop down list values are already hard coded. There are only 12 districts so the jQuery Autocomplete UI control isn't populated by code.
The solution is much easier. Because I had to wade through other posts where it was assumed the control was being dynamically loaded, wasn't finding what I needed and then finally figured it out.
So where you have HTML as below, setting the selected index is set like this, note the -input part, which is in addition to the drop down id:
$('#project-locationSearch-dist-input').val('1');
<label id="lblDistDDL" for="project-locationSearch-input-dist" title="Select a district to populate SPNs and PIDs or enter a known SPN or PID." class="control-label">District</label>
<select id="project-locationSearch-dist" data-tabindex="1">
<option id="optDistrictOne" value="01">1</option>
<option id="optDistrictTwo" value="02">2</option>
<option id="optDistrictThree" value="03">3</option>
<option id="optDistrictFour" value="04">4</option>
<option id="optDistrictFive" value="05">5</option>
<option id="optDistrictSix" value="06">6</option>
<option id="optDistrictSeven" value="07">7</option>
<option id="optDistrictEight" value="08">8</option>
<option id="optDistrictNine" value="09">9</option>
<option id="optDistrictTen" value="10">10</option>
<option id="optDistrictEleven" value="11">11</option>
<option id="optDistrictTwelve" value="12">12</option>
</select>
Something else figured out about the Autocomplete control is how to properly disable/empty it. We have 3 controls working together, 2 of them mutually exclusive:
//SPN
spnDDL.combobox({
select: function (event, ui) {
var spnVal = spnDDL.val();
//fire search event
$('#project-locationSearch-pid-input').val('');
$('#project-locationSearch-pid-input').prop('disabled', true);
pidDDL.empty(); //empty the pid list
}
});
//get the labels so we have their tool tips to hand.
//this way we don't set id values on each label
spnDDL.siblings('label').tooltip();
//PID
pidDDL.combobox({
select: function (event, ui) {
var pidVal = pidDDL.val();
//fire search event
$('#project-locationSearch-spn-input').val('');
$('#project-locationSearch-spn-input').prop('disabled', true);
spnDDL.empty(); //empty the spn list
}
});
Some of this is beyond the scope of the post and I don't know where to put it exactly. Since this is very helpful and took some time to figure out, it's being shared.
Und Also ... to enable a control like this, it's (disabled, false) and NOT (enabled, true) -- that also took a bit of time to figure out. :)
The only other thing to note, much in addition to the post, is:
/*
Note, when working with the jQuery Autocomplete UI control,
the xxx-input control is a text input created at the time a selection
from the drop down is picked. Thus, it's created at that point in time
and its value must be picked fresh. Can't be put into a var and re-used
like the drop down list part of the UI control. So you get spnDDL.empty()
where spnDDL is a var created like var spnDDL = $('#spnDDL); But you can't
do this with the input part of the control. Winded explanation, yes. That's how
I have to do my notes or 6 months from now I won't know what a short hand note means
at all. :)
*/
//district
$('#project-locationSearch-dist').combobox({
select: function (event, ui) {
//enable spn and pid drop downs
$('#project-locationSearch-pid-input').prop('disabled', false);
$('#project-locationSearch-spn-input').prop('disabled', false);
//clear them of old values
pidDDL.empty();
spnDDL.empty();
//get new values
GetSPNsByDistrict(districtDDL.val());
GetPIDsByDistrict(districtDDL.val());
}
});
All shared because it took too long to learn these things on the fly. Hope this is helpful.

You can select dropdown option value by name
// deom
jQuery("#option_id").find("option:contains('Monday')").each(function()
{
if( jQuery(this).text() == 'Monday' )
{
jQuery(this).attr("selected","selected");
}
});

$('select#myselect option[value="ab"]')

either can be used to get the selected option value
$('#dropdownID').on('change', function () {
var dropdownselected=$("#dropdownID option:selected").val();
});
or
$('#dropdownID').on('change', function () {
var dropdownselected=this.selectedOptions[0].value;
});