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Dynamically adding onchange function to drop down with jQuery

I have a couple of drop down boxes with ids country1, country2, ... When the country is changed in a drop down the value of the country shoudl be displayed in an alert box.
if I add the onchange handler for one box like this it works fine:
$('#country1') .live('change', function(e){
var selectedCountry = e.target.options[e.target.selectedIndex].value;
alert(selectedCountry);
});
But I need to do this dynamically for all drop down boxes so I tried:
$(document).ready(function() {
$('[id^=country]') .each(function(key,element){
$(this).live('change', function(e){
var selectedCountry = e.target.options[e.target.selectedIndex].value;
alert(selectedCountry);
});
});
});
This doesn't work. No syntax error but just nothing happens when the seleted country is changed. I am sure that the each loop is performed a couple of times and the array contains the select boxes.
Any idea on that?
Thanks,
Paul

The reason .live() existed was to account for elements not present when you call the selector.
$('[id^=country]') .each(function(key,element){ iterates over elements that have an id that starts with country, but only those that exist when you run the selector. It won't work for elements that you create after you call .each(), so using .live() wouldn't do you much good.
Use the new style event delegation syntax with that selector and it should work:
$(document).on('change', '[id^=country]', function(e) {
// ...
});
Replace document with the closest parent that doesn't get dynamically generated.
Also, consider adding a class to those elements along with the id attribute.

Instead of incremental ids I'd use a class. Then the live method is deprecated but you may use on with delegation on the closest static parent or on document otherwise.
$('#closestStaticParent').on('change', '.country', function() {
// this applies to all current and future .country elements
});
You don't need an each loop this way; plus events are attached to all the elements in the jQuery collection, in this case all .country elements.

Display number of checked checkboxes in jQuery

I am quite new to jQuery, I think this might be quite easy for many of you, but I can't seem to make it work. How can I display the number of checkboxes so that the value increases or decreases.
i tried the following but with the number in the span tag remains 0: http://jsfiddle.net/yunowork/NTwxc/
Thanks

You should listen to the change event:
$('input[type=checkbox]').on('change', function(){
var number = $('input[type=checkbox]:checked').length;
$('.totalchecked').text(number);
});
http://jsfiddle.net/NTwxc/7/
Note that val is used for getting/setting values of form elements, for other elements like span element, text or html methods should be used.

Number of checked checkboxes:
$(":checkbox:checked").length
http://api.jquery.com/checked-selector/
edit: I see in your fiddle that you already had that. I'll leave it there, since that's actually the answer to "how to display the number of checked checkboxes"...
The problem is that you're not updating and looking to see how many are checked. You need to re-run that function whenever any of the items are checked.
$(":checkbox").change(function () {
// update the span with $(":checkbox:checked").length ...
});

You shouldn't be setting .val of a span, but .text.
Also, you need to update it every time the checked state changes.
function calc() {
$('.totalchecked').text($(':checkbox:checked').length);
}
$(calc);
$(':checkbox').change(calc);
Demo

Here we are!
$('input[type="checkbox"]').change(function() {
$('.totalchecked').empty().text($('input[type="checkbox"]:checked').size());
});
http://jsfiddle.net/toroncino/PTvG8/

Problems: .val() is for form elements only. To set the content of an element, use .text() or .html() if you are inserting HTML. Second problem is that you need to register a listener to "change" events. Otherwise, the value won't update.
Updated solution: http://jsfiddle.net/NTwxc/4/
$("input[type=checkbox]").change(function(){
var number = $('input[type=checkbox]:checked').length;
$(".totalchecked").text(number);
});
​
By the way, I would personally prefer input[type=checkbox]rather than :checkbox. The former works for both CSS and jQuery.

Jquery binding to keyup

I'm having some problems binding to the keyup event of a textarea control. I'm trying the below
var shortDescInput = $('nobr:contains("Short Description")').closest('tr').find($('textarea[title="Short Description"]'));
// this doesn't work
shortDescInput.bind('keyup', function () {
countShortDescChars();
});
// Nor this
shortDescInput.keyup(function () {
countShortDescChars();
});
Am I missing something here that's really obvious? This is working for other controls, for example binding events to radiobuttons. I've checked and I'm defiantly selecting the right textarea with
var shortDescInput = $('nobr:contains("Short Description")').closest('tr').find($('textarea[title="Short Description"]'));
I just never seem to get the keyup event....

find($('textarea[title="Short Description"]')) is highly inefficient. For your purposes, find should take a selector as it's argument.
When you pass in a jQuery object to find, jQuery first queries the DOM from the top and finds all elements that match that selector. Then, find loops through all of these results until it finds one that matches the specified parents.
You should, instead, use:
find('textarea[title="Short Description"]')
Also, use .on instead of .bind. .bind is set to be deprecated in future releases for it's inefficiency.
shortDescInput.on("keyup", countShortDescChars);
And the revised code:
$(function () {
var shortDescInput = $('nobr:contains("Short Description")').closest('tr').find('textarea[title="Short Description"]');
shortDescInput.on("keyup", countShortDescChars);
});

To verify that a selector is working use .length with a console.log() or old fashioned alert() :
var shortDescInput = $('nobr:contains("Short Description")').closest('tr').find('textarea[title="Short Description"]');
alert(shortDescInput.length);
You can also go step by step to identify the one not returning anything :
alert($('nobr:contains("Short Description")').length);
alert($('nobr:contains("Short Description")').closest('tr').length);
alert($('nobr:contains("Short Description")').closest('tr').find('textarea[title="Short Description"]').length);
Second try. using .on() instead of .bind() :
shortDescInput.on('keyup',function(){countShortDescChars();});

So I played along with your fiddle and...
There IS something wrong with your selector.
First I remove the script tags from the js part.
then remove the script tag in your html cause it broke the fiddle.
Switched to jQuery 1.8.0 cause MooTools is not what we want.
added shortDescInput = $('textarea'); after your giant selector, event is triggered!
Added again shortDescInput = $('textarea'); in your function to make the counter work.
So again, let's now try to figure why your selector is not working :-)
Edit:
Found it!
I replaced your .closest() with .parent().next() because I kind of think .closest() was targeting the parent .
var shortDescInput = $('nobr:contains("Short Description")').parent().next().find('textarea[title="Short Description"]');

The problem is that at least in the fiddle, the <tr> wasn't in a <table>and so it was removed from the DOM by the browser. Wrapping the <tr> in a <table> made the fiddle work.
Demo: http://jsfiddle.net/kNkXE/9/

How to gain access to an element on the same level in the DOM?

<div id="dad">
<img id="mum">
<input>
</div>
With jQuery, how could i get access to the input element, get is value or set it for example? I can't work out how to access something on the same level.. and i dont want to be using ID's, just parent/child nodes so i can use the code for loads of dad div's
Thanks!

an addition to Zed,
$(this).parent().children('input');
if you give a name to your input field then you can easily select throughout the others,
$(this).parent().children('input[name=my_input]');
then you can give any value as:
$(this).parent().children('input[name=my_input]').val('any value');
Sinan.

var myEl = $("#dad").children(":input");

$(this).parent().children() ?

Try this, to find the first child input element:
jQuery("div").find("input:first")

If i understand question, you would like achieve input from mum leve?
So try $("#mum ~ input")...
BTW, great site to search jquery function by category http://visualjquery.com/ +nice example.

I guess you want to find siblings (node with same depth and same parent and in DOM tree)
$(el).next() - next element (sibling) for all elements in the set
$(el).nextAll - all following siblings
$(el).nextUntil - all following siblings, stop on some condition (not including first "bad match").
Besides, you have next adjacent selector (+) and next sibling selector.
The same about prev, prevAll and prevUntil.
And you even have a siblings method.
Check this out.

How to clear all <div>s’ contents inside a parent <div>?

I have a div <div id="masterdiv"> which has several child <div>s.
Example:
<div id="masterdiv">
<div id="childdiv1" />
<div id="childdiv2" />
<div id="childdiv3" />
</div>
How to clear the contents of all child <div>s inside the master <div> using jQuery?

jQuery's empty() function does just that:
$('#masterdiv').empty();
clears the master div.
$('#masterdiv div').empty();
clears all the child divs, but leaves the master intact.

jQuery('#masterdiv div').html('');

Use jQuery's CSS selector syntax to select all div elements inside the element with id masterdiv. Then call empty() to clear the contents.
$('#masterdiv div').empty();
Using text('') or html('') will cause some string parsing to take place, which generally is a bad idea when working with the DOM. Try and use DOM manipulation methods that do not involve string representations of DOM objects wherever possible.

I know this is a jQuery related question, but I believe someone might get here expecting a pure Javascript solution. So, if you were trying to do this using js, you could use the innerHTML property and set it to an empty string.
document.getElementById('masterdiv').innerHTML = '';

jQuery recommend you use ".empty()",".remove()",".detach()"
if you needed delete all element in element, use this code :
$('#target_id').empty();
if you needed delete all element, Use this code:
$('#target_id').remove();
i and jQuery group not recommend for use SET FUNCTION like .html() .attr() .text() , what is that? it's IF YOU WANT TO SET ANYTHING YOU NEED
ref :https://learn.jquery.com/using-jquery-core/manipulating-elements/

If all the divs inside that masterdiv needs to be cleared, it this.
$('#masterdiv div').html('');
else, you need to iterate on all the div children of #masterdiv, and check if the id starts with childdiv.
$('#masterdiv div').each(
function(element){
if(element.attr('id').substr(0, 8) == "childdiv")
{
element.html('');
}
}
);

The better way is :
$( ".masterdiv" ).empty();

$("#masterdiv div").text("");

$("#masterdiv > *").text("")
or
$("#masterdiv").children().text("")

$('#div_id').empty();
or
$('.div_class').empty();
Works Fine to remove contents inside a div

You can use .empty() function to clear all the child elements
$(document).ready(function () {
$("#button").click(function () {
//only the content inside of the element will be deleted
$("#masterdiv").empty();
});
});
To see the comparison between jquery .empty(), .hide(), .remove() and .detach() follow here http://www.voidtricks.com/jquery-empty-hide-remove-detach/

When you are appending data into div by id using any service or database, first try it empty, like this:
var json = jsonParse(data.d);
$('#divname').empty();

$("#masterdiv div[id^='childdiv']").each(function(el){$(el).empty();});
or
$("#masterdiv").find("div[id^='childdiv']").each(function(el){$(el).empty();});

try them if it help.
$('.div_parent .div_child').empty();
$('#div_parent #div_child').empty();