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!!

Get a select box by name and set another select box by same name?

I am building a fairly complex form-- I need to copy some data between one and another and I am using jQuery to do this. The only road block I am running into is setting the state.
I have two drop downs, one us using the full state name as the value and the other is using the state abbreviation as the value. The names are the same-
so on form 1 it looks like
<option value="Illinois">Illinois</option>
and form 2 it looks like
<option value="IL">Illinois</option>
Each form has its own unique css selector. How can I set the selected value of form 2 to match what is in form 1 using jQuery?
I do not have any control over the forms, just need to manipulate the input. Have tried using a name selector in jQuery, but I'm not having any luck.
Thank you.

You can do something like this
<select id="fullName">
<option value="Maryland" data-abbr="MD">Maryland</option>
<option value="Illinois" data-abbr="IL">Illinois</option>
<option value="Delaware" data-abbr="DE">Delaware</option>
</select>
<select id="abbr">
<option value="MD">Maryland</option>
<option value="IL">Illinois</option>
<option value="DE">Delaware</option>
</select>
And your jQuery
$('body').on('change', '#fullName', function(){
var abbr = $(this).find('option:selected').data('abbr');
$('#abbr').val(abbr);
});

Try this
<form id="form1" name="form1">
<select name="states" onchange="changeselect(this)">
<option value="option1">option1</option>
<option value="option2">option2</option>
<option value="option3">option3</option>
<option value="option4">option4</option>
<option value="option5">option5</option>
</select>
</form>
<form id="form2" name="form2">
<select name="states">
<option value="opt1">option1</option>
<option value="opt2">option2</option>
<option value="opt3">option3</option>
<option value="opt4">option4</option>
<option value="opt5">option5</option>
</select>
</form>
function changeselect(elem)
{
var value1 = $(elem).val();
$('#form2 select option').removeAttr('selected');
$('#form2').find('select option').each(function(){
var value2 = $(this).html();
if(value1 == value2)
{
var selected = $(this).attr('value');
$('#form2 select').val(selected);
}
});
}

If you create 2 arrays which exactly correspond with one another:
var StateNames = ['Alabama','Alaska','Arizona','Arkansas','California','Colorado','Connecticut','Delaware','Florida','Georgia','Hawaii','Idaho','Illinois','Indiana','Iowa','Kansas','Kentucky','Louisiana','Maine','Maryland','Massachusetts','Michigan','Minnesota','Mississippi','Missouri','Montana','Nebraska','Nevada','New Hampshire','New Jersey','New Mexico','New York','North Carolina','North Dakota','Ohio','Oklahoma','Oregon','Pennsylvania','Rhode Island','South Carolina','South Dakota','Tennessee','Texas','Utah','Vermont','Virginia','Washington','West Virginia','Wisconsin','Wyoming'];
var StateAbbreviations = ['AL','AK','AZ','AR','CA','CO','CT','DE','FL','GA','HI','ID','IL','IN','IA','KS','KY','LA','ME','MD','MA','MI','MN','MS','MO','MT','NE','NV','NH','NJ','NM','NY','NC','ND','OH','OK','OR','PA','RI','SC','SD','TN','TX','UT','VT','VA','WA','WV','WI','WY'];
You can:
get the value from the first option list;
find that value's index in the first array; (hint: use indexOf)
use the same index to find out what the corresponding abbreviation is in the second array;
use the returned abbreviation to locate the correct option in the second option list

How to select an option with CasperJS

I try to set select option attribute to selected. But I try to avoid using nth-child in CasperJS because there are bugs in PhantomJS's nth-child.
So I try to use this as the subtitution of jQuery(css_path).
function setSelectedCountry(i){
window.__utils__.echo("i :"+i);
var query = "//*[#id='cboCountry']/optgroup[2]/option["+i+"]";
__utils__.getElementByXPath(query).setAttribute("selected","selected");
}
But, when I evaluate that code by this way
this.evaluate(setSelectedCountry, 5);
The select option is not changed.
Moreover, when I try to trigger onblur() using
document.getElementById("cboCountry").onblur();
inside setSelectedCountry() funtion, there were nothing happened.
Why this happened?
Also, when I try to call the function with XPath expression, and the other one is using CSS selector, I got undefined error returned from CasperJS.
I use this function :
function getCityName(i){
var query = "//*[#id='cboCity']/option["+i+"]";
return __utils__.getElementByXPath(query).innerText;
}
then I got the other one:
function setSelectedCountry(i){
var query = "#cboCountry > optgroup:nth-child(3) > option:nth-child("+i+")";
jQuery(query).attr("selected", "selected").blur();
}
When I try to run both of them, then this is what I've got
PAGE.ERROR: TypeError: 'undefined' is not an object (evaluating
'__utils__.getElementByXPath(query).innerText')
Can you give me suggestions?
[EDITED]
Here is my markup :
This one for cboCountry select option :
<select name="cboCountry" id="cboCountry" onkeypress="return selectItem();" onkeyup="event.cancelbubble=true;return false;" onkeydown="return handleKey();" onfocus="activeList=this;this.enteredText='';" onchange="//hs.DropCity();" onblur="hs.DropCity();"
class="txtBox">
<option value="">-- --Select-- --</option>
<optgroup label="Popular Destinations">
<option value="MA05110065">Indonesia</option>
<option value="MA05110067">Malaysia</option>
<option value="MA05110069">Singapore</option>
<option value="MA05110001">Thailand</option>
</optgroup>
<optgroup label="Other Destinations">
<option value="MA05110083">Afghanistan</option>
<option value="MA05110124">Albania</option>
<option value="MA05110133">Algeria</option>
<option value="MA05110186">American Samoa</option>
<option value="MA05110103">Andorra</option>
<option value="MA05110014">Angola</option>
<option value="MA05110135">Anguilla (UK)</option>
<option value="MA05110136">Antigua and Barbuda</option>
<option value="MA05110171">Argentina</option>
<option value="MA05110206">Armenia</option>
<option value="MA05110183">Venezuela</option>
<option value="MA05110070">Vietnam</option>
<option value="MA05110013">Western Sahara</option>
<option value="MA05110082">Yemen</option>
<option value="MA05110027">Zambia</option>
<option value="MA05110028">Zimbabwe</option>
</optgroup>
</select>
And this one for cboCity select option :
<select name="cboCity" id="cboCity" onkeypress="return selectItem();" onkeyup="event.cancelbubble=true;return false;" onkeydown="return handleKey();" onfocus="activeList=this;this.enteredText='';" onchange="//hs.DropLocation();" onblur="hs.DropLocation();"
class="txtBox">
<option value="">-- --Select-- --</option>
<option value="">-- Select --</option>
<option value="MA02022810">Ambarawa</option>
<option value="MA09090008">Ambon</option>
<option value="MA08090042">Anyer</option>
<option value="MA02022861">Wonosobo</option>
<option value="MA06060051">Yogyakarta</option>
</select>

The problem is the distinction between property and attribute. Browsers usually don't re-evaluate attributes when you change them in the DOM. In those cases, you would need to change the property behind that attribute on the DOM element.
In this case, you need to change the selected index. The select element has the selectedIndex property that you can change to the intended option which you can get through option.index:
function setSelectedCountry(i){
__utils__.echo("i :"+i);
var opt = "//*[#id='cboCountry']/optgroup[2]/option["+i+"]";
var select = document.getElementById('cboCountry');
select.selectedIndex = __utils__.getElementByXPath(opt).index;
select.onblur(); // or `onchange()`
}
See this answer for more information on the option index.
"//*[#id='cboCity']/option["+i+"]" cannot work, because this expression will match options that are direct children of a #cboCity element, but you have an optgroup inbetween. Either use "//*[#id='cboCity']//option["+i+"]" or "//*[#id='cboCity']/optgroup/option["+i+"]".

How to change "size" of select when click on select?

sorry for my bad english, i have a problem with select :
<form name="reg" style="width:700px;" action="#" method="post">
<p align="center">
<select onChange="reg(this.options[this.selectedIndex].value)" size="1">
<option selected value="250">Select the Reg</option>
<option value="0">Reg 1</option>
<option value="1">Reg 2</option>
<option value="2">Reg 3</option>
<option value="3">Reg 4</option>
<option value="4">Reg 5</option>
<option value="5">Reg 6</option>
<option value="6">Reg 7</option>
<option value="7">Reg 8</option>
<option value="8">Reg 9</option>
<option value="9">Reg 10</option>
</select>
</p>
</form>
I would like that when i click on select, the size of select changes in size="5", because when the document load the size is size="1" (and this is good) but if i click on select, it shows all ten options, and this is the problem...
While, if i click on select, the size changes, is most beautiful.
EDIT
In future the form could have more 250 options, so is important that when the document load size is 1, and when i click the size is 5 ....
the size must be "5" only when the select show options, and when an option is selected the size must be 1.
The problem is that i don't know how made it, maybe with jquery? or only with css?
Can you help me?
Thanks!

Here is a working solution for your problem:
add focus event handler to the select list with id='selRegs'
set the size attribute to 6 (5 will show 4 options + the "Select the Reg" option)
after option is changed the size will be reset to 1
remove focus from select
https://jsfiddle.net/juaxo8zm/8/
$(document).ready(function () {
var initPos = $("#yourDiv").position();
console.log("init: ");
console.log(initPos);
$('#selRegs').focus(function () {
$('#selRegs').attr("size", "6");
$("#yourDiv").css({
position: "absolute",
top: initPos.top,
left: initPos.left
});
});
$('#selRegs').change(function () {
console.log("selected");
$('#selRegs').attr("size", "1");
$("#selRegs").blur();
$("#yourDiv").css({
position: "static"
});
});
});
I use jQuery for this:
.change()
.focus()
.attr(param1, param2)
.blur()
.position()

Try this:
<select size="1"
onfocus='this.size=5;'
onblur='this.size=1;'
onchange='this.size=1; this.blur();'
>

Use the HTML onclick="myFunction()" event tag from the HTML select tag, or use jQuery click() handler if you want to declare the event handler at the javascript level (I mean if you want add the additional event from javascript).
I mean you have a choice - add the extra event dispatch code in the HTML tag source code or add it from the javascript/jQuery level.
The problem is that onChange() event dispatch doesn't get called until too late for your need (it gets called after a user selects a value).
You need to get notified the moment the button for the drop-down menu is clicked so you can change the selected value (default) value.
In your click function handler change the selectedIndex property and set it to the the index of the line that contains "5"

You should use click event on select
$('select').on('click',function(){
$(this).attr('size',5)
});

Just use javascript :
<select id='sel' onfocus='changesize();' onchange='changesize2();' size='1'>
<option selected value="250">Select the Reg</option>
<option value="0">Reg 1</option>
<option value="1">Reg 2</option>
<option value="2">Reg 3</option>
<option value="3">Reg 4</option>
<option value="4">Reg 5</option>
<option value="5">Reg 6</option>
<option value="6">Reg 7</option>
<option value="7">Reg 8</option>
<option value="8">Reg 9</option>
<option value="9">Reg 10</option>
</select>
<script>
function changesize(){
document.getElementById('sel').size = '5';
}
function changesize2(){
document.getElementById('sel').size = '1';
document.getElementById('sel').blur();
}
</script>
Demo : http://codepen.io/anon/pen/zxbRZb

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;
});