Develop Reference

HTML make <option> invalid

I have the following piece of code in a contact form for a site I am designing:
<select id="Category" name="Category">
<option value="0" selected="selected" disabled>Category</option>
<option value="1">General Info</option>
<option value="2">Booking</option>
<option value="3">Auditions</option>
</select>
I would like set the menu such that the user cannot leave category as the selected option. Is there any way to do this with HTML? If not, how would I do it with JavaScript?
Thank you

According to the HTML5 spec,
Constraint validation: If the element has its required attribute specified, and either none of the option elements in
the select element's list of options have their
selectedness set to true, or the only option element in
the select element's list of options with its
selectedness set to true is the placeholder label option,
then the element is suffering from being missing.
If a select element has a required attribute
specified, does not have a multiple attribute specified, and
has a display size of 1; and if the value of the first
option element in the select element's list of
options (if any) is the empty string, and that option
element's parent node is the select element (and not an
optgroup element), then that option is the select
element's placeholder label option.
Therefore, you can use
<select id="Category" name="Category" required>
<option value="" selected disabled>Category</option>
<option value="1">General Info</option>
<option value="2">Booking</option>
<option value="3">Auditions</option>
</select>

When the user click on any option, he can´t return the first one back. But he can submit form without change, then you need to validate via JS.
It's quite simple,
function validate() {
var select = document.getElementById('Category');
return !select.value == 0;
}
And the form in HTML:
<form onsubmit="return validate()">...</form>

Will disabling select work for you?
<select id="Category" name="Category" disabled>
<option value="0" selected="selected">Category</option>
...
</select>
Or maybe disabling all but selected option will work for you (as shown here: https://stackoverflow.com/a/23428851/882073)

Ideally, you would simply remove the selected attribute from disabled options on the server side when generating the HTML document to begin with.
Otherwise, if you are using JQuery, this can be done fairly easily with:
$('#Category').find('option:not([disabled])').first().prop('selected', true);
Add this to your ondomready event handler. This will force the first non-disabled option to be selected for this select element regardless of its options' selected attributes. The disadvantage of this method is that it will prevent the selected attribute from being able to be used at all with this select element.
On the other hand, if you are trying to create category headers within a select element, you should consider using an optgroup element instead, since that is the correct semantic markup for this:
<select id="Category" name="Category">
<optgroup label="Category">
<option value="1">General Info</option>
<option value="2">Booking</option>
<option value="3">Auditions</option>
</optgroup>
</select>

How to get selected option with raw javascript

HTML
<form>
<select name="select">
<option value="option1">Option 1</option>
<option value="option2">Option 2</option>
</select>
<input type="submit" onclick="processForm(this.form)">
</form>
JS
function processForm(form) {
console.log(form)
}
I can successfully get the form as HTMLElement but cannot seem to find easy way to get selected value

Since you're sending the form object itself on submit, getting data is easy in vanilla JS. Modify your function to:
function processForm(form) {
var selected = form.select
console.log(selected.value)
}
Note that select is not some special property of the form, it's just because that's what you gave the name attribute for the select element.

Dynamically change text in php

hey guys i am building a form in which i want when a user select an option from the dropdown menus a text to be displayed and calculate the price.
The dropdown menu is:
<select id="recipient" name="recipient" tabindex="6" class="selmenu">
<option value="staff">Site Staff</option>
<option value="editor">Editor-in-Chief</option>
<option value="technical">Tech Department</option>
<option value="pr">Public Relations</option>
<option value="support">General Support</option>
</select>
and the other dropdown menu is:
<select id="recipient" name="recipient" tabindex="6" class="selmenu">
<option value="one">1</option>
<option value="two">2</option>
<option value="three">3</option>
<option value="four">4</option>
<option value="five">5</option>
</select>
What i want to do is when the user selects something from the first and the second menu i want a textfield to change dynamically... can anyone point me the way?

only ajax/jquery could do that in combination of php step might be...
onchange of any dropdown make a ajax request to php script.
return the json response from php script
use this response to either manipulate your form or display data on page.

you don't need to use php for this, it can all be done with jquery/javscript
an example using jquery is below (i had to rename your second select as you had re-used an ID):
$('.selmenu').change(function() {
$('#output').text($('#recipient option:selected').text() + ' ' + $('#recipient2 option:selected').text());
})
output is the id of your textbox.
on a select value being changed, output will be filled with the selected value in both select controls

how to get the value from javascript code to jsp scriptlet with in the same jsp page

below is my code (1.jsp)
<html>
<head>
<script type="text/javascript">
function changeFunc() {
var selectBox = document.getElementById("selectBox");
var selectedValue = selectBox.options[selectBox.selectedIndex].value;
document.write("\n value is"+selectedValue);
}
</script>
</head>
<body>
<form method="post" action="SampServlet">
<select id="selectBox" name="selurl" onchange="changeFunc();">
<option value="1">Option #1</option>
<option value="2">Option #2</option>
</select>
</form>
</body>
</html>
Here I have inserted this code into a jsp page.And getting the value of "selectedValue" from javascript to scriptlet with in the same jsp like this.
<% String val=(String)request.getParameter("selurl");
System.out.println("\n selected value is:"+val); %>
I am getting selected value as null as output. And if I print javascript selectedValue parameter it is giving me correct output i.e.,output as the option selected.But in scriptlet am getting null.Where is the error.I included all headers and directives.Please help me.

In your web browser you have only html, javascript and css. All JSP code is meant to be run on the server. So you get only the output of the jsp file. And after this you cannot change the jsp code.

Use submit Button to get Your Selected value at same page and
no need any function,no need onsubmit.
for example:
<form method="post" action="">
<select id="selectBox" name="selurl">
<option value="1">Option #1</option>
<option value="2">Option #2</option>
</select>
<input type="submit" value="Submit" name="sub">
//use scriplet tag
<% String r=request.getParameter("sub");
if(r.equals("Submit"){
String s=request.getParameter("selurl");
System.out.println("selected value is "+s);
}%>
</form>

Your select element should have a name attribute and you must use that name in request.getParameter()
<select id="selectBox" name="selurl"">
<option value="1">Option #1</option>
<option value="2">Option #2</option>
</select>
String val = request.getParameter("mySelect");
EDIT:
If you want the server request to be made on the select element's onchange event, you must Ajax.
Using jQuery,
$.post('SampServlet', {selectedValue: selectedValue}, function(data) {
//Update view
});

You're missing the <submit> button.
<form method="post" action="SampServlet">
<select id="selectBox" name="selurl" onchange="changeFunc();">
<option value="1">Option #1</option>
<option value="2">Option #2</option>
</select>
<input type="submit" /> <!-- MISSING!! -->
</form>
Add the button and click on it to submit the form to your servlet with the selected value sent as selurl. Please, note that your form's action attribute is pointing to SampServlet which seems to be a servlet. For jsps we usually have something like action="page.jsp" in the form.
EDIT:
If you want to post the form automatically when the user selects a value from the drop-down just set your onchange to: (you won't even need the <submit> button then)
onchange="this.form.submit()"

jquerymobile Add select menus dynamically

I have a set of dropboxes
code is
<fieldset data-role="controlgroup" data-type="horizontal">
<!--<legend> </legend>-->
<select name="select-widget" id="select-widget">
<option value="Widget">Widget</option>
</select>
<select name="select-nbl" id="select-nbl">
<option value="NBL">NBL</option>
<option value="HSM">HSM</option>
<option value="TERR">TERR</option>
<option value="KEY_ACCOUNT">KEY ACCOUNT</option>
</select>
<select name="select-level-focus" id="select-level-focus">
<option value="LEVEL">LEVEL</option>
<option value="FOCUS">FOCUS</option>
</select>
<select name="select-wdg" id="select-wdg">
<option value="WDG">WDG</option>
</select>
<select name="select-wds" id="select-wds">
<option value="WDS">WDS</option>
</select>
</fieldset>
No I want to remove exixsting selectbox or add new select box to it on change of "select-nbl" or "select-levelfocus"
How to do it using jquerymobile

This has little to do with jQuery mobile, that's merely a mobile framework. The event listeners and DOM manipulation you want to do here is still handled by jQuery.
Anyways, how do you do it?
Well, you have your event listeners:
$('#select-nbl').change(function() {
#Do something
});
And you can hide stuff:
$('#select-wdg').parents('.ui-select').hide();
The use of parents() is to take care of the extra styling jQuery mobile puts in there.
You can't easily add select boxes to jQuery mobile, but if they're hidden, you can show them.
$('#select-wdg').parents('.ui-select').show();
All this is action: http://jsfiddle.net/luhn/Vgc4g/9/