Develop Reference

Converting a JavaScript function to jQuery - Select option list

This is literally the first time I've worked with jQuery and I've read the entire chapter in my textbook but am finding a hard time wrapping my head around it. I'm attempting to convert a JavaScript function (a simple option selection drop-down list) to jQuery. I've attempted a few lines of code that I've gotten from the book or from w3schools and api.query but to no avail. I'll try to make this quick and simple, I just cannot understand jQuery for some reason.
What I've attempted usually doesn't work. Before my option list works fine, then I tried experimenting but I didn't get too far.
I also apolgize for the vagueness of the question, I'd appreciate any help!
Here's something I've tried:
$(document).ready( function () {
var c = ???
if ($(c...
calc.js and index.html below it
function selectedCountry() {
var c = document.getElementById("countryChooser").value;
var message;
if (c == "nothing") { //if they selected the default option, error pops up.
alert("Please select a country.");
} else if (c == "usa") {
message = "United States of America";
document.getElementById("count").innerHTML = "Your country is: " + message;
} else if (c == "canada") {
message = "Canada";
document.getElementById("count").innerHTML = "Your country is: " + message;
} else {
message = "Mexico";
document.getElementById("count").innerHTML = "Your country is: " + message;
}
}
<script src = "calc.js"></script> <!--JavaSript link -->
<select name="countrylist" id="countryChooser" onchange="selectedCountry()">
<option value="nothing">Select a country</option>
<option value="usa">United States of America</option>
<option value="canada">Canada</option>
<option value="mexico">Mexico</option>
</select>
<p id="count"></p>

Through jQuery you can do it like below:-
Example:-
$(document).ready(function(){
$('#countryChooser').change(function(){ // on change of select
if($(this).val()!=='nothing'){ // if selected value is some country
$('#count').html("Your country is: "+$("#countryChooser option:selected").text()); // get country name and add it to paragraph
}else{
$('#count').html("");
alert('Please select a country.'); // alert for selecting a country
}
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<select name="countrylist" id="countryChooser">
<option value="nothing">Select a country</option>
<option value="usa">United States of America</option>
<option value="canada">Canada</option>
<option value="mexico">Mexico</option>
</select>
<p id="count"></p>

Get an element by id:
var c = $('#countryChooser');
Get the value of this input/select element
var value = c.val();
Set the html of an element using the element id
$('#count').html('some html');
or set the text (html is not parsed this way)
$('#count').text('some html');
You can also handle the events with jQuery
$(document).ready(function() {
$('#countryChooser').on('change', function(event) {
// this is the DOM element with the id 'countryChooser'
// same as the native: var val = this.value;
var val = $(this).val();
// ...
});
});

I have bind the onchange() event of your select list inside the jQuery(document).ready() method. check this out-
// Updated code--
$(document).ready(function (){
$('#countryChooser').on('change' ,function () {
if(this.selectedIndex){
$('#count').html("Your country is: "+ this.options[this.selectedIndex].text);
}else{
$('#count').html("");
alert("Please select a country.");
}
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src = "calc.js"></script> <!--JavaSript link -->
<select name="countrylist" id="countryChooser">
<option value="nothing">Select a country</option>
<option value="usa">United States of America</option>
<option value="canada">Canada</option>
<option value="mexico">Mexico</option>
</select>
<p id="count"></p>

$('#countryChooser').change(function(){
var selectedCountry = $(this).val();
if(selectedCountry == 'nothing'){
console.log('Select A country');
}
else{
$('#count').html('Your country is '+$('#countryChooser option:selected').text());
}
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<!--JavaSript link -->
<select name="countrylist" id="countryChooser" >
<option value="nothing">Select a country</option>
<option value="usa">United States of America</option>
<option value="canada">Canada</option>
<option value="mexico">Mexico</option>
</select>
<p id="count"></p>
Please check the code might help you out
thanks

Option selected value onchange

Hello this is my current code:
<select id="link_course">
<option value="">Select Course</option>
<option value="ALL">ALL</option>
<option value="BSIT" selected>BSIT</option>
<option value="BSA">BSA</option>
<option value="BSBA">BSBA</option>
<option value="BSHRTM">BSHRTM</option>
</select>
<script>
$("#link_course").change(function()
{
document.location.href = "home.php?course=" + $(this).val();
});
</script>
If you click any of those options, for example BSBA, it will go to home.php?course=BSBA, and also you can see that the selected attribute is on the option BSIT. What I wanted to do is whenever I click another link, for example BSHRTM, the selected attribute will go to BSHRTM like it would be <option value="BSHRTM" selected>BSHRTM</option>. Any thoughts?

You can do selection via JavaScript :
function getQueryVariable(variable)
{
var query = window.location.search.substring(1);
var vars = query.split("&");
for (var i=0;i<vars.length;i++) {
var pair = vars[i].split("=");
if(pair[0] == variable){return pair[1];}
}
return(false);
}
if(getQueryVariable('course') != false) {
$('#link_course option[value="' + getQueryVariable('course') + '"]').prop('selected', true);
}
Reference

After loading the new page, you need to run JavaScript code to set the value on the correct item from the list.

Use window.location.hrefto get current URL. Then check on which page is user currently on and finally select corresponding option.
if(window.location.href.indexOf('home.php?course=BSHRTM)') != -1) {
$('select#link_course option[value=BSHRTM]').attr("selected","selected");
}
To avoid code duplication see Parse query string in JavaScript

You should do it in PHP:
<option value="BSHRTM" <?php if($course == 'BSHRTM') echo 'selected';?>>
Supposing that you previsously set $course = $_GET['course'];

Jquery to modify URL based on an IF?

I have a URL that does a filter and spits out some products the structure looks like below:
/Products/Catalogue/tabid/102/andmode/1/Default.aspx?catfilter=185,223
Now on this there is a sort function and if I was to use this with out filtering as above the URL would look like the below:
/Products/Catalogue.aspx?orderby=price&desc=1&psize=9
If I currently try and filter and then sort, the sort overwrites myfilter, so the filter becomes null and void.
So what I need it do is be aware that IF i have a filter then append the sorting after 'catfilter=' part in the URL so the URL would then look like
/Products/Catalogue/tabid/102/andmode/1/Default.aspx?catfilter=8,188&orderby=man&desc=0&psize=36
The gotcha is that there is not always going to be a filter added in which case the URL would be:
/Products/Catalogue.aspx
<select id="listSort" class="NormalTextBox SortCatalogue" onchange="location = this.options[this.selectedIndex].value + '&' + getElementById('listLength')[getElementById('listLength').selectedIndex].value.split('?')[1] + document.getElementById('searchstrdiv').innerHTML.replace('amp;','');">
<option value="?orderby=name&desc=0&">Sort by</option>
<option value="?orderby=price&desc=0">Lowest price</option>
<option value="?orderby=price&desc=1">Highest price</option>
<option value="?orderby=man&desc=0">Brand A-Z</option>
<option value="?orderby=man&desc=1">Brand Z-A</option>
<option value="?orderby=name&desc=0">Title A-Z</option>
<option value="?orderby=name&desc=1">Title Z-A</option>
<option value="?orderby=ref&desc=0">Code asc</option>
<option value="?orderby=ref&desc=1">Code desc</option>
</select>
<span style="text-align:right">Page size</span>
<select id="listLength" class="NormalTextBox PageLength" onchange="location = this.options[this.selectedIndex].value + '&' + getElementById('listSort')[getElementById('listSort').selectedIndex].value.split('?')[1] + document.getElementById('searchstrdiv').innerHTML.replace('amp;','');">
<option value="?psize=9&foo">Page size</option>
<option value="?psize=6">6 per page</option>
<option value="?psize=9">9 per page</option>
<option value="?psize=18">18 per page</option>
<option value="?psize=36">36 per page</option>
</select>
<script type="text/javascript">
var searchString = window.location.search.substring(1);
var i, val;
var params = searchString.replace('?','&').split('&');
var pgsize,pgorder,pdesc,searchstr;
pgsize = 9;
pgorder = 'name';
pdesc = 0;
searchstr='';
for (i=0;i<params.length;i++) {
val = params[i].split('=');
if(val[0]== "psize")
pgsize=val[1];
else if(val[0]== "orderby")
pgorder=val[1];
else if(val[0]== "desc")
pdesc=val[1];
else if((val[0]).toLowerCase()== "search") {
searchstr=val[1];
}
}
document.getElementById('listLength').value='?psize=' + pgsize;
document.getElementById('listSort').value ='?orderby=' + pgorder + '&desc=' + pdesc;
if(searchstr!='') {
searchstr =decodeURIComponent(searchstr.replace(/\+/g, '%20'));
document.getElementById('searchstrdiv').innerHTML= '&search=' + searchstr ;
document.getElementById('searchtxthdrleft').innerHTML= 'Results for "' ;
document.getElementById('searchtxthdrright').innerHTML= '"' ;
document.getElementById('searchtxt').innerHTML = searchstr;
}
</script>

Ok lets take a step back from the problem. I think you need to add a bit more structure instead of haphazardly adding and removing bits of url code here and there :)
You have tagged the post as jQuery so i'm going to use that although you haven't actually used it in your posted code.
The whole idea is going to be around creating a JavaScript object and using it as a lightweight dictionary, and the jQuery .param() function which will encode it for us at the end.
Lets change the markup to this:
<select id="listSort" class="NormalTextBox SortCatalogue">
<option value="nameDesc">Sort by</option>
<option value="priceAsc">Lowest price</option>
<option value="priceDesc">Highest price</option>
<option value="manAsc">Brand A-Z</option>
<option value="manDesc">Brand Z-A</option>
<option value="nameAsc">Title A-Z</option>
<option value="nameDesc">Title Z-A</option>
<option value="refAsc">Code asc</option>
<option value="refDesc">Code desc</option>
</select>
<span style="text-align:right">Page size</span>
<select id="listLength" class="NormalTextBox PageLength">
<option value="9">Page size</option>
<option value="6">6 per page</option>
<option value="9">9 per page</option>
<option value="18">18 per page</option>
<option value="36">36 per page</option>
</select>
<input type="text" id="searchstr">
<button id="searchbutton">Search!</button>
As you will see I've also thrown in a textbox and a button as you refer to searchstr in your code.
Instead of encoding and extracting we are just going to store some parseable values in the select options. We're also going to use an unobtrusive javascript technique by using the ID to attach an onchange handler rather than injecting the javascript into the markup (this will be added later on).
Now we need to write some JavaScript code that can build us a querystring. Instead of directly building a querystring though we will be making a javascript object. Then later on that will be used to generate the query string.
I've written a search function that just displays the query string we generated rather than redirect the user.
I've also added in some event handlers so this is triggered as your code was triggering.
function getFiltersAsQueryString() {
var $listSort = $("#listSort"),
$listLength = $("#listLength"),
$searchQuery = $("#searchstr");
queryStringDict = {};
// extract page size
queryStringDict["psize"] = $listLength.find("option:selected").val();
// extract sort order and direction
var selectedItem = $listSort.find("option:selected").val();
queryStringDict["orderby"] = /^[a-z]*/.exec(selectedItem)[0];
queryStringDict["desc"] = /Desc$/.exec(selectedItem) == "Desc" ? 1 : 0;
// extract search
queryStringDict["search"] = $searchQuery.val();
return $.param(queryStringDict);
}
function searchWithFilters() {
// normally you would do a window.location here to redirect
alert(getFiltersAsQueryString());
}
$(document).ready(function () {
// wire up our handlers
$("#listSort").change(searchWithFilters);
$("#listLength").change(searchWithFilters);
$("#searchbutton").click(searchWithFilters);
});
And then at the end of the day when you put all this together you get this:
http://jsfiddle.net/rtpHarry/pdhCF/3/
I don't think this is quite a complete solution yet.
Need to add in the cat filter
Probably want to preselect the controls based on the query string?
I just wanted to post this to see if its going in the right direction.

Hugly helpful thank you, ended up going with this some JS and Jquery in up to come up with the complete solution:
<script type="text/javascript">
var searchString = window.location.search.substring(1);
var i, val;
var params = searchString.replace('?','&').split('&');
var pgsize,pgorder,pdesc,searchstr,catfilter;
pgsize = 9;
pgorder = 'name';
pdesc = 0;
searchstr='';
for (i=0;i<params.length;i++) {
val = params[i].split('=');
if(val[0]== "psize")
pgsize=val[1];
else if(val[0]== "orderby")
pgorder=val[1];
else if(val[0]== "desc")
pdesc=val[1];
else if(val[0]== "catfilter")
catfilter=val[1];
else if((val[0]).toLowerCase()== "search")
{ searchstr=val[1]; }
}
document.getElementById('listLength').value='?psize=' + pgsize;
document.getElementById('listSort').value ='?orderby=' pgorder '&desc=' + pdesc;
if(searchstr!='')
{
searchstr =decodeURIComponent(searchstr.replace(/\+/g, '%20'));
document.getElementById('searchstrdiv').innerHTML= '&search=' + searchstr ;
document.getElementById('searchtxthdrleft').innerHTML= 'Results for "' ;
document.getElementById('searchtxthdrright').innerHTML= '"' ;
document.getElementById('searchtxt').innerHTML = searchstr;
}
if(catfilter)
{
document.getElementById('searchstrdiv').innerHTML= document.getElementById('searchstrdiv').innerHTML + '&catfilter=' + catfilter ;
}
</script>
<script type="text/javascript">
$(document).ready(function(){
$('.SortCatalogue').removeAttr('onchange');
$('.SortCatalogue').change(function() {newURL();});
$('.PageLength').removeAttr('onchange');
$('.PageLength').change(function() {newURL();});
function newURL()
{
var newParams = document.getElementById('listSort') [document.getElementById('listSort').selectedIndex].value + '&' + document.getElementById('listLength') [document.getElementById('listLength').selectedIndex].value.split('?')[1] + document.getElementById('searchstrdiv').innerHTML.replace('amp;','');
var oldPathname = location.pathname;
oldPathname = oldPathname.replace('/desc/','/').replace('/orderby/', '/');
document.location.href = oldPathname + newParams;
}
});
</script>

Dynamically update form action based on selected <option>

So, this is what I am trying to do.. I want a dropdown in HTML with a submit button that changes based on the value of the dropdown.
So, when I have this:
<select name="sizes" id="select13">
<option value="All">All</option>
<option value="20x30">20x30</option>
<option value="30x30">30x30</option>
...
</select>
What I need is a button that checks what the value is. If value = 20x30 then use URL www.example.com/20x30
If value is 30x30 then use URL www.example.com/30x30
I am far from a PHP expert, so anyone that is able to set me off in the right direction would be a life saver :)

some simple Javascript would suffice:
<form id="FORM_ID" action="DEFAULT_ACTION">
<select name="sizes" id="select13">
<option value="All">All</option>
<option value="20x30">20x30</option>
<option value="30x30">30x30</option>
</select>
</form>
<script type="text/javascript">
document.getElementById('select13').onchange = function(){
document.getElementById('FORM_ID').action = '/'+this.value;
}
</script>

You might try this:
Javascript:
function goto() {
window.location = "http://www.example.com/"+document.getElementById('select13').value;
}
HTML:
<select name="sizes" id="select13">
<option value="All">All</option>
<option value="20x30">20x30</option>
<option value="30x30">30x30</option>
</select>
<button onclick='goto()'>Go</button>
When you click on the 'GO' button it redirects to example.com/(the selected value).
Here's a JSFiddle with an exmaple.
EDIT to fit your comment:
function goto() {
var selection = document.getElementById('select13').value;
if (selection != 'All') {
//window.location = "http://www.example.com/"+selection;
alert("http://www.example.com/" + selection);
} else {
alert("Error: You must pick something");
}
}
Also, if you want to submit a form and then do the redirection. The PHP code would be as follows:
<?php
//Process your form without echoing anything before the header function.
if($_REQUEST['sizes'] != 'All'){
header('location:http://example.com/'.$_REQUEST['sizes']);
}
else{
header('location:http://example.com/form.php');
}

You'll need an onchange event for your dropdown:
document.getElementById("select13").onchange = function() {
var currentVal = this.value;
if (currentVal == "20x30") {
//do stuff
}
}

How do I programmatically set the value of a select box element using JavaScript?

I have the following HTML <select> element:
<select id="leaveCode" name="leaveCode">
<option value="10">Annual Leave</option>
<option value="11">Medical Leave</option>
<option value="14">Long Service</option>
<option value="17">Leave Without Pay</option>
</select>
Using a JavaScript function with the leaveCode number as a parameter, how do I select the appropriate option in the list?

You can use this function:
function selectElement(id, valueToSelect) {
let element = document.getElementById(id);
element.value = valueToSelect;
}
selectElement('leaveCode', '11');
<select id="leaveCode" name="leaveCode">
<option value="10">Annual Leave</option>
<option value="11">Medical Leave</option>
<option value="14">Long Service</option>
<option value="17">Leave Without Pay</option>
</select>
Optionally if you want to trigger onchange event also, you can use :
element.dispatchEvent(new Event('change'))

If you are using jQuery you can also do this:
$('#leaveCode').val('14');
This will select the <option> with the value of 14.
With plain Javascript, this can also be achieved with two Document methods:
With document.querySelector, you can select an element based on a CSS selector:
document.querySelector('#leaveCode').value = '14'
Using the more established approach with document.getElementById(), that will, as the name of the function implies, let you select an element based on its id:
document.getElementById('leaveCode').value = '14'
You can run the below code snipped to see these methods and the jQuery function in action:
const jQueryFunction = () => {
$('#leaveCode').val('14');
}
const querySelectorFunction = () => {
document.querySelector('#leaveCode').value = '14'
}
const getElementByIdFunction = () => {
document.getElementById('leaveCode').value='14'
}
input {
display:block;
margin: 10px;
padding: 10px
}
<select id="leaveCode" name="leaveCode">
<option value="10">Annual Leave</option>
<option value="11">Medical Leave</option>
<option value="14">Long Service</option>
<option value="17">Leave Without Pay</option>
</select>
<input type="button" value="$('#leaveCode').val('14');" onclick="jQueryFunction()" />
<input type="button" value="document.querySelector('#leaveCode').value = '14'" onclick="querySelectorFunction()" />
<input type="button" value="document.getElementById('leaveCode').value = '14'" onclick="getElementByIdFunction()" />
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

function setSelectValue (id, val) {
document.getElementById(id).value = val;
}
setSelectValue('leaveCode', 14);

Not answering the question, but you can also select by index, where i is the index of the item you wish to select:
var formObj = document.getElementById('myForm');
formObj.leaveCode[i].selected = true;
You can also loop through the items to select by display value with a loop:
for (var i = 0, len < formObj.leaveCode.length; i < len; i++)
if (formObj.leaveCode[i].value == 'xxx') formObj.leaveCode[i].selected = true;

I compared the different methods:
Comparison of the different ways on how to set a value of a select with JS or jQuery
code:
$(function() {
var oldT = new Date().getTime();
var element = document.getElementById('myId');
element.value = 4;
console.error(new Date().getTime() - oldT);
oldT = new Date().getTime();
$("#myId option").filter(function() {
return $(this).attr('value') == 4;
}).attr('selected', true);
console.error(new Date().getTime() - oldT);
oldT = new Date().getTime();
$("#myId").val("4");
console.error(new Date().getTime() - oldT);
});
Output on a select with ~4000 elements:
1 ms
58 ms
612 ms
With Firefox 10. Note: The only reason I did this test, was because jQuery performed super poorly on our list with ~2000 entries (they had longer texts between the options).
We had roughly 2 s delay after a val()
Note as well: I am setting value depending on the real value, not the text value.

document.getElementById('leaveCode').value = '10';
That should set the selection to "Annual Leave"

I tried the above JavaScript/jQuery-based solutions, such as:
$("#leaveCode").val("14");
and
var leaveCode = document.querySelector('#leaveCode');
leaveCode[i].selected = true;
in an AngularJS app, where there was a required <select> element.
None of them works, because the AngularJS form validation is not fired. Although the right option was selected (and is displayed in the form), the input remained invalid (ng-pristine and ng-invalid classes still present).
To force the AngularJS validation, call jQuery change() after selecting an option:
$("#leaveCode").val("14").change();
and
var leaveCode = document.querySelector('#leaveCode');
leaveCode[i].selected = true;
$(leaveCode).change();

Short
This is size improvement of William answer
leaveCode.value = '14';
leaveCode.value = '14';
<select id="leaveCode" name="leaveCode">
<option value="10">Annual Leave</option>
<option value="11">Medical Leave</option>
<option value="14">Long Service</option>
<option value="17">Leave Without Pay</option>
</select>

The easiest way if you need to:
1) Click a button which defines select option
2) Go to another page, where select option is
3) Have that option value selected on another page
1) your button links (say, on home page)
<a onclick="location.href='contact.php?option=1';" style="cursor:pointer;">Sales</a>
<a onclick="location.href='contact.php?option=2';" style="cursor:pointer;">IT</a>
(where contact.php is your page with select options. Note the page url has ?option=1 or 2)
2) put this code on your second page (my case contact.php)
<?
if (isset($_GET['option']) && $_GET['option'] != "") {
$pg = $_GET['option'];
} ?>
3) make the option value selected, depending on the button clicked
<select>
<option value="Sales" <? if ($pg == '1') { echo "selected"; } ?> >Sales</option>
<option value="IT" <? if ($pg == '2') { echo "selected"; } ?> >IT</option>
</select>
.. and so on.
So this is an easy way of passing the value to another page (with select option list) through GET in url. No forms, no IDs.. just 3 steps and it works perfect.

function foo(value)
{
var e = document.getElementById('leaveCode');
if(e) e.value = value;
}

Suppose your form is named form1:
function selectValue(val)
{
var lc = document.form1.leaveCode;
for (i=0; i<lc.length; i++)
{
if (lc.options[i].value == val)
{
lc.selectedIndex = i;
return;
}
}
}

Should be something along these lines:
function setValue(inVal){
var dl = document.getElementById('leaveCode');
var el =0;
for (var i=0; i<dl.options.length; i++){
if (dl.options[i].value == inVal){
el=i;
break;
}
}
dl.selectedIndex = el;
}

Why not add a variable for the element's Id and make it a reusable function?
function SelectElement(selectElementId, valueToSelect)
{
var element = document.getElementById(selectElementId);
element.value = valueToSelect;
}

Most of the code mentioned here didn't worked for me!
At last, this worked
window.addEventListener is important, otherwise, your JS code will run before values are fetched in the Options
window.addEventListener("load", function () {
// Selecting Element with ID - leaveCode //
var formObj = document.getElementById('leaveCode');
// Setting option as selected
let len;
for (let i = 0, len = formObj.length; i < len; i++){
if (formObj[i].value == '<value to show in Select>')
formObj.options[i].selected = true;
}
});
Hope, this helps!

You most likely want this:
$("._statusDDL").val('2');
OR
$('select').prop('selectedIndex', 3);

If using PHP you could try something like this:
$value = '11';
$first = '';
$second = '';
$third = '';
$fourth = '';
switch($value) {
case '10' :
$first = 'selected';
break;
case '11' :
$second = 'selected';
break;
case '14' :
$third = 'selected';
break;
case '17' :
$fourth = 'selected';
break;
}
echo'
<select id="leaveCode" name="leaveCode">
<option value="10" '. $first .'>Annual Leave</option>
<option value="11" '. $second .'>Medical Leave</option>
<option value="14" '. $third .'>Long Service</option>
<option value="17" '. $fourth .'>Leave Without Pay</option>
</select>';

I'm afraid I'm unable to test this at the moment, but in the past, I believe I had to give each option tag an ID, and then I did something like:
document.getElementById("optionID").select();
If that doesn't work, maybe it'll get you closer to a solution :P