Develop Reference

How to get the value of option with attribute selected

I'm trying to get the value of the option which have the attribute "selected" to compare it to the current option selected.
function onChangeOption(opt) {
var update_value = opt.value;
var selectedValue = '???'; // get selected attribute
if (update_value != selectedValue) {
// Do some things
}
}
<select class="form-control" onchange="onChangeOption(this)">
<!-- I wanna got the content of option selected=selected-->
<option selected="selected" value="1">1</option>
<option value="2">2</option>
</select>

// save initial selected value to a variable
var initSelected = $('.form-control option:selected').val();
$('select').on('change', function() {
// check if the selected value is the same as the initial one was
if(this.value == initSelected) {
console.log('same values');
} else {
console.log('not same values');
}
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<select class="form-control">
<option selected="selected" value="1">1</option>
<option value="2">2</option>
</select>

Just add change event listener.And get the selected value.You can achieve comparision between selected value and changed value by maintaining an array.Like below.
values = []//creates an array
select = document.querySelector('#myselect');
values.unshift(select.value);
//console.log(values);
select.addEventListener('change',function(){
update_value = this.value;
console.log(this.value);
if (update_value != values[0]) {
// alert('Not matched');
console.log('Not matched');
}
else{
//alert('Matched');
console.log('Matched')
}
});
<select class="form-control" id="myselect">
<option selected="selected" value="1"> 1 </option>
<option value="2"> 2 </option>
</select>

I think alexis actually wants something more like this:
function onChangeOption(opt) {
var update_value = opt.value;
var options = document.getElementsByTagName("option");
if (options[0].getAttribute("selected")=="selected") {
var selectedValue = options[0].value;
} else {
var selectedValue = options[1].value;
}
if (update_value != selectedValue) {
// If the selected option's value is not equal to the value of the option with the attribute "selected", then do... (this way, you can change the attribute to any of the options!)
console.log(selectedValue);
}
}
<select class="form-control" onchange="onChangeOption(this)">
<option selected="selected" value="1">1</option>
<option value="2">2</option>
</select>
Comment the result and if you need anything else. Glad to help.

You can always store previously selected values, if you want to access them somehow later on: working example.
HTML:
<select id="mySelect" class="form-control" onchange="onChangeOption(this)">
<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>
<p>Previous: <span id="prev"></span></p>
<p>Current: <span id="curr"></span></p>
JS:
var selectElem = document.getElementById("mySelect");
var prev = document.getElementById("prev");
var curr = document.getElementById("curr");
var allEverSelected = [ selectElem.value ];
selectElem.addEventListener("change", function(evt){
allEverSelected.push( this.value );
prev.innerHTML = allEverSelected[allEverSelected.length - 2];
curr.innerHTML = allEverSelected[allEverSelected.length - 1];
});
To access default value, just get the <select> value after DOM loads.
selected attribute on <option> tag exist only to make other than first <option> element inside <select> default option, i.e.:
<select>
<option value="1">1</option>
<option selected value="2">2</option>
</select>
Above select's default value is 2.

I think this is the one what you want. Try it.
function onChangeOption(opt) {
var update_value = opt.value;
console.log(update_value);
var selectedValue;// = '???'; // get selected attribute
// I think this is the one you want
//If you want to select the HTML element,
selectedValue=document.querySelector("option[value='"+update_value+"']");
console.log(selectedValue);
//
if (update_value != selectedValue) {
// Do some things
}
}
//onChangeOption(document.querySelector('form'));
function start(){
while(typeof document.querySelector('form')!=typeof {}){}
onChangeOption(document.querySelector('.form-control'));
}
<body onload="start()">
<select class="form-control" onchange="onChangeOption(this)">
<option selected="selected" value="1">1</option>
<!-- I wanna got this -->
<option value="2">2</option>
</select></body>

Event listener inside a function

I have a select on my page:
<select id='cat'>
<option value='a'>A</option>
<option value='b'>B</option>
<option value='all'>all</option>
</select>
With a javascript function that handles which options have to be displayed:
function funcName(aList) {
// populates the options for the select tag
$("#cat").on("change", function(){
// some computation;
});
// uses aList to update some div data
}
What I'm trying to do is if the selected option is all, I have to display everything in aList, otherwise based on the selected option I have to display only the related options. Is my usage of onchange event correct?
Initially I thought of making aList global, but after some reading on globals in JS, I got to know it is not a very good practice.
Thanks in advance!
UPDATE: aList contains some string values.

$(function () {
$("#ddl").change(function () {
var selectedText = $(this).find("option:selected").text();
var selectedValue = $(this).val();
var assignedRoleId = new Array();
alert("Selected Text: " + selectedText + " Value: " + selectedValue);
if(selectedValue== "all")
{
$("#ddl option").each(function()
{
if(this.value=="all")
{
assignedRoleId.push();
}
else
{
assignedRoleId.push(this.value);
assignedRoleId.push(" ");
$("#selected").html(assignedRoleId);
}
});
}
});
});
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
Select something:
<select id="ddl">
<option value="">select one</option>
<option value="a">a</option>
<option value="b">b</option>
<option value="all">all</option>
</select>
<div id="selected">
</div>

Display items of drop down based on each other

1) I have two drop downs with exactly the same values. I want the drop down 2 to display the values based on the selection of items of drop down 1. So the selected index of drop down 2 will be equal to or more than the selected index of drop down 1. ( this code is working)
but When I add one more drop down and based on its items the other two dropdowns should behave as:
2) If I select TCD in the first Dropdown and change to value B in the second dropdown the value should be B in the third dropdown too but If I select BCD from the first dropdown it should retain the values of other two dropdown from the previous selection.( should not go back to A)
The first part is working but the second part is having issues.
Fiddle : 1) http://jsfiddle.net/wtLm4805/2/
Fiddle with three dropdowns : 2) http://jsfiddle.net/wtLm4805/3/
while (select2.firstChild) {
select2.removeChild(select2.firstChild);
}
for (var i = 0; i < select1.options.length; i++) {
var o = document.createElement("option");
o.value = select1.options[i].value;
o.text = select1.options[i].text;
(i < select1.selectedIndex)
? o.disabled = true
: o.disabled = false ;
select2.appendChild(o);
}
Where am I going wrong ?

You can go somewhere along these lines
var typeValue = 'TCD'; // default initialisation
$('#Type').change(function(){
var value = $(this).val();
console.log(value);
if(value == 'TCD')
{
typeValue = 'TCD';
// change something in other selects too
}
else if(value == 'MCD')
{
typeValue = 'MCD';
}
else if(value == 'BCD')
{
$('#SELECTA').val('B');
$('#SELECTB').val('B');
typeValue = 'BCD';
}
});
$('#SELECTA').change(function(){
var value = $(this).val();
console.log(value);
if(typeValue = 'TCD')
{
$('#SELECTB').val(value);
}
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<select name="Type" id="Type" >
<option value="TCD">TCD</option>
<option value="MCD" >MCD</option>
<option value="BCD" >BCD</option>
</select>
<select id="SELECTA" class="SELECTA">
<option value="A">A</option>
<option value="B">B</option>
<option value="C">C</option>
<option value="D">D</option>
</select>
<select id="SELECTB" class="SELECTB" >
<option value="A">A</option>
<option value="B">B</option>
<option value="C">C</option>
<option value="D">D</option>
</select>

Since you have only one element with class SELECTA and one with class SELECTB, these will always be undefined:
var select1 = document.getElementsByClassName("SELECTA")[1];
var select2 = document.getElementsByClassName("SELECTB")[1];
var select1 = document.getElementsByClassName("SELECTA")[2];
var select2 = document.getElementsByClassName("SELECTB")[2];
If you're trying to target the options, you could move the classes to the options themselves, or you could reference them like this:
document.getElementsByClassName("SELECTA")[0].options[1]
Not sure why you're deleting/adding items to the SELECTB element, but is this what you're going for?
function clickButton() {
var Type= document.getElementById('Type');
var select1= document.getElementById('SELECTA');
var select2= document.getElementById('SELECTB');
if(Type.value === 'TCD') {
for(var i = 0 ; i < select1.options.length ; i++) {
select2.options[i].disabled= i < select1.selectedIndex;
}
select2.value= select1.value;
}
else {
for(var i = 0 ; i < select2.options.length ; i++) {
select2.options[i].disabled= false;
}
}
}
<select name="Type" id="Type" onchange="clickButton()">
<option value="TCD">TCD</option>
<option value="MCD">MCD</option>
<option value="BCD">BCD</option>
</select>
<select id="SELECTA" onchange="clickButton()">
<option value="A">A</option>
<option value="B">B</option>
<option value="C">C</option>
<option value="D">D</option>
</select>
<select id="SELECTB">
<option value="A">A</option>
<option value="B">B</option>
<option value="C">C</option>
<option value="D">D</option>
</select>

Can I pass multiple Id's inside a document.getelementbyID?

I have a form which has got 45 dropdownlist and I m using the bottom code for its
validation.
how can I use only one function of bottom code to do validation for all of my 45 dropdownlist ??
Here is the Function
function Validate()
{
var e = document.getElementById("dropdownlistone");
var strUser = e.options[e.selectedIndex].value;
var strUser1 = e.options[e.selectedIndex].text;
if(strUser==0)
{
alert("Please select a user");
}
}
----- HTML CODE
<select id="dropdownlistone">
<option value="0">Select</option>
<option value="1">test1</option>
<option value="2">test2</option>
<option value="3">test3</option>
</select>
<input type="button" onClick="Validate()" value="select"/>

This is a case when you need to use classes. Then use querySelectorAll method:
function Validate() {
var e = document.querySelectorAll(".dropdownlistone");
for (var i = 0; i < e.length; i++) {
var strUser = e[i].options[e[i].selectedIndex].value;
var strUser1 = e[i].options[e[i].selectedIndex].text;
if (strUser == 0) {
alert("Please select a user");
return;
}
}
}
Demo: http://jsfiddle.net/cwNaH/
And here is one more example with more user friendly validation messages: http://jsfiddle.net/cwNaH/1/

You can use DOM Method getElementsByTagName for select box and set an data-attr to "validate" for those whom you want to validate, if you dont want it to be validate simply don't add the above mentioned attribute.
Ex. HTML
<select id="sel1" data-attr="validate">
<option value="0">Select</option>
<option value="1">test1</option>
<option value="2">test2</option>
<option value="3">test3</option>
</select>
<select id="sel2" data-attr="validate">
<option value="0">Select</option>
<option value="1">test1</option>
<option value="2">test2</option>
<option value="3">test3</option>
</select>
JavaScript
function validate()
{
var ele = document.getElementsByTagName("select");
for(var i=0;i<ele.length;i++)
{
if(ele.getAttribute("data-attr") && ele.getAttribute("data-attr")=='validate')
{
// you have all 47 select boxes whoose data-attr is validate
// each select box will be in ele[i]
var value= ele[i].options[ele[i].selectedIndex].value;
var text= ele[i].options[ele[i].selectedIndex].text;
alert( value+ " : " + text);
}
}
}

Changing the selected option of an HTML Select element

In my HTML, I have a <select> with three <option> elements. I want to use jQuery to check each option's value against a Javascript var. If one matches, I want to set the selected attribute of that option. How would I do that?

Vanilla JavaScript
Using plain old JavaScript:
var val = "Fish";
var sel = document.getElementById('sel');
document.getElementById('btn').onclick = function() {
var opts = sel.options;
for (var opt, j = 0; opt = opts[j]; j++) {
if (opt.value == val) {
sel.selectedIndex = j;
break;
}
}
}
<select id="sel">
<option>Cat</option>
<option>Dog</option>
<option>Fish</option>
</select>
<button id="btn">Select Fish</button>
jQuery
But if you really want to use jQuery:
var val = 'Fish';
$('#btn').on('click', function() {
$('#sel').val(val);
});
var val = 'Fish';
$('#btn').on('click', function() {
$('#sel').val(val);
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<select id="sel">
<option>Cat</option>
<option>Dog</option>
<option>Fish</option>
</select>
<button id="btn">Select Fish</button>
jQuery - Using Value Attributes
In case your options have value attributes which differ from their text content and you want to select via text content:
<select id="sel">
<option value="1">Cat</option>
<option value="2">Dog</option>
<option value="3">Fish</option>
</select>
<script>
var val = 'Fish';
$('#sel option:contains(' + val + ')').prop({selected: true});
</script>
Demo
But if you do have the above set up and want to select by value using jQuery, you can do as before:
var val = 3;
$('#sel').val(val);
Modern DOM
For the browsers that support document.querySelector and the HTMLOptionElement::selected property, this is a more succinct way of accomplishing this task:
var val = 3;
document.querySelector('#sel [value="' + val + '"]').selected = true;
Demo
Knockout.js
<select data-bind="value: val">
<option value="1">Cat</option>
<option value="2">Dog</option>
<option value="3">Fish</option>
</select>
<script>
var viewModel = {
val: ko.observable()
};
ko.applyBindings(viewModel);
viewModel.val(3);
</script>
Demo
Polymer
<template id="template" is="dom-bind">
<select value="{{ val }}">
<option value="1">Cat</option>
<option value="2">Dog</option>
<option value="3">Fish</option>
</select>
</template>
<script>
template.val = 3;
</script>
Demo
Angular 2
Note: this has not been updated for the final stable release.
<app id="app">
<select [value]="val">
<option value="1">Cat</option>
<option value="2">Dog</option>
<option value="3">Fish</option>
</select>
</app>
<script>
var App = ng.Component({selector: 'app'})
.View({template: app.innerHTML})
.Class({constructor: function() {}});
ng.bootstrap(App).then(function(app) {
app._hostComponent.instance.val = 3;
});
</script>
Demo
Vue 2
<div id="app">
<select v-model="val">
<option value="1">Cat</option>
<option value="2">Dog</option>
<option value="3">Fish</option>
</select>
</div>
<script>
var app = new Vue({
el: '#app',
data: {
val: null,
},
mounted: function() {
this.val = 3;
}
});
</script>
Demo

None of the examples using jquery in here are actually correct as they will leave the select displaying the first entry even though value has been changed.
The right way to select Alaska and have the select show the right item as selected using:
<select id="state">
<option value="AL">Alabama</option>
<option value="AK">Alaska</option>
<option value="AZ">Arizona</option>
</select>
With jquery would be:
$('#state').val('AK').change();

You can change the value of the select element, which changes the selected option to the one with that value, using JavaScript:
document.getElementById('sel').value = 'bike';​​​​​​​​​​
DEMO

Markup
<select id="my_select">
<option value="1">First</option>
<option value="2">Second</option>
<option value="3">Third</option>
</select>
jQuery
var my_value = 2;
$('#my_select option').each(function(){
var $this = $(this); // cache this jQuery object to avoid overhead
if ($this.val() == my_value) { // if this option's value is equal to our value
$this.prop('selected', true); // select this option
return false; // break the loop, no need to look further
}
});
Demo

I want to change the select element's selected option's both value & textContent (what we see) to 'Mango'.
Simplest code that worked is below:
var newValue1 = 'Mango'
var selectElement = document.getElementById('myselectid');
selectElement.options[selectElement.selectedIndex].value = newValue1;
selectElement.options[selectElement.selectedIndex].textContent = newValue1;
Hope that helps someone. Best of luck.
Up vote if this helped you.

I used almost all of the answers posted here but not comfortable with that so i dig one step furter and found easy solution that fits my need and feel worth sharing with you guys.
Instead of iteration all over the options or using JQuery you can do using core JS in simple steps:
Example
<select id="org_list">
<option value="23">IBM</option>
<option value="33">DELL</option>
<option value="25">SONY</option>
<option value="29">HP</option>
</select>
So you must know the value of the option to select.
function selectOrganization(id){
org_list=document.getElementById('org_list');
org_list.selectedIndex=org_list.querySelector('option[value="'+id+'"]').index;
}
How to Use?
selectOrganization(25); //this will select SONY from option List
Your comments are welcome. :) AzmatHunzai.

Test this Demo
Selecting Option based on its value
var vals = [2,'c'];
$('option').each(function(){
var $t = $(this);
for (var n=vals.length; n--; )
if ($t.val() == vals[n]){
$t.prop('selected', true);
return;
}
});
Selecting Option based on its text
var vals = ['Two','CCC']; // what we're looking for is different
$('option').each(function(){
var $t = $(this);
for (var n=vals.length; n--; )
if ($t.text() == vals[n]){ // method used is different
$t.prop('selected', true);
return;
}
});
Supporting HTML
<select>
<option value=""></option>
<option value="1">One</option>
<option value="2">Two</option>
<option value="3">Three</option>
</select>
<select>
<option value=""></option>
<option value="a">AAA</option>
<option value="b">BBB</option>
<option value="c">CCC</option>
</select>

Excellent answers - here's the D3 version for anyone looking:
<select id="sel">
<option>Cat</option>
<option>Dog</option>
<option>Fish</option>
</select>
<script>
d3.select('#sel').property('value', 'Fish');
</script>

After a lot of searching I tried #kzh on select list where I only know option inner text not value attribute,
this code based on select answer I used it to change select option according to current page urlon this format
http://www.example.com/index.php?u=Steve
<select id="sel">
<option>Joe</option>
<option>Steve</option>
<option>Jack</option>
</select>
<script>
var val = window.location.href.split('u=')[1]; // to filter ?u= query
var sel = document.getElementById('sel');
var opts = sel.options;
for(var opt, j = 0; opt = opts[j]; j++) {
// search are based on text inside option Attr
if(opt.text == val) {
sel.selectedIndex = j;
break;
}
}
</script>
This will keeps url parameters shown as selected to make it more user friendly and the visitor knows what page or profile he is currently viewing .

You just write the code
var theVal = 1;
$('#variable_id').val(theVal).trigger('change');

I used this after updating a register and changed the state of request via ajax, then I do a query with the new state in the same script and put it in the select tag element new state to update the view.
var objSel = document.getElementById("selectObj");
objSel.selectedIndex = elementSelected;
I hope this is useful.

selectElement is a html <select> element.
Increment the value:
selectElement.selectedIndex++
Decrement the value:
selectElement.selectedIndex--

var accHos = document.getElementById("accHos");
function showName(obj) {
accHos.selectedIndex = obj.selectedIndex;
}
div {
color: coral;
}
select {
margin-left: 20px;
margin-bottom: 8px;
min-width: 120px;
}
<div>Select Account Number:</div>
<select id="accNos" name="" onchange="showName(this);">
<option value="">Select Account</option>
<option value="">1052021</option>
<option value="">2052021</option>
<option value="">3052021</option>
<option value="">4052021</option>
<option value="">5052021</option>
</select>
<div>Account Holder Name:</div>
<select id="accHos" name="" disabled>
<option value="">--Name--</option>
<option value="">Suhan</option>
<option value="">Cesur</option>
<option value="">Hopper</option>
<option value="">Rachel</option>
<option value="">Arya</option>
</select>
<!-- Just for my referece -->

Slightly neater Vanilla.JS version. Assuming you've already fixed nodeList missing .forEach():
NodeList.prototype.forEach = Array.prototype.forEach
Just:
var requiredValue = 'i-50332a31',
selectBox = document.querySelector('select')
selectBox.childNodes.forEach(function(element, index){
if ( element.value === requiredValue ) {
selectBox.selectedIndex = index
}
})