Michael Gaigg: Über UI/UX Design

29Mar0

jQuery: Handle Dropdown (select), Checkboxes and Radio selections

Posted by Michael Gaigg

Almost daily I work with lists, be it dropdown, checkbox or radio selections. I need to select values, submit selections, hide/show containers depending on the selection etc.

I tend to forget all these cool jQuery notations that make every programmers life easier. How nice would it be to have a little cheat sheet? So I decided to summarize my findings (and share them with you).

Obviously jQuery is powerful and gives you a multitude of possibilities so this list is neither exhaustive nor covers all possible application scenarios. Mix, match, combine and extend the samples as you wish and feel free to post your additional solutions in the comments section.

See the test page.

Dropdown

I'm using the following sample list:

<select id="ddlCategories"> 
   <option>- Select a category -</option>
   <option value="books" selected="selected">Books</option>
   <option value="videos">Videos</option>
   <option value="dvds">DVDs</option>
</select>

Get value of selected item

Pure and simple, despite what you might read in other tutorials:

alert("Selected value: " + $("#ddlCategories").val());

Change text of a particular item

Let's target item with value 'videos':

$("#ddlCategories option[value='videos']").text("Videos and tapes");

Change color of a particular item

This could be useful to show that the category is currently unavailable or a certain item is out of stock.

$("#ddlCategories option[value='videos']").css("color", "#CCC");

Get number of options

Don't forget to subtract options that don't count, e.g. the empty "- Select a category -" option.

alert("Number of options: " + ($("#ddlCategories option").length - 1));

Set a particular option

Set the option 'videos' to be the selected item.

$("#ddlCategories option[value='videos']").attr("selected", "selected");

Checkboxes

Our sample checkbox list:

<div id="chkCategoriesContainer">
	<input type="checkbox" name="chkCategories" value="none" checked="checked" />None<br/>
	<input type="checkbox" name="chkCategories" value="books" />Books<br/>
	<input type="checkbox" name="chkCategories" value="videos" />Videos<br/>
	<input type="checkbox" name="chkCategories" value="dvds" />DVDs<br/>
</div>

Check all items in the checkbox list

This could be invoked e.g. through a link named 'Check all'.

$("input[name='chkCategories']").attr("checked","checked");

Uncheck all items in the checkbox list

Same here, uncheck all, a very common requirement.

$("input[name='chkCategories']").removeAttr("checked");

Make the second item being checked

List is zero-based, so the second item is nth(1) 😉

$("input[name='chkCategories']:nth(1)").attr("checked","checked");

Show the value of each checked item (requires a container!)

In this case we simply alert the value, but we could might as well write it to another output field, container or whatever you may wish.

$('#chkCategoriesContainer :checkbox:checked').each(function() {
	alert($(this).val());
	//$('#outputField').append(', '+$(this).val());
});

Radio

Our sample list again:

<div id="rdoCategoriesContainer">
	<input type="radio" name="rdoCategories" value="none" checked="checked" />None<br/>
	<input type="radio" name="rdoCategories" value="books" />Books<br/>
	<input type="radio" name="rdoCategories" value="videos" />Videos<br/>
	<input type="radio" name="rdoCategories" value="dvds" />DVDs<br/>
</div>

Get value of checked item

alert("Selected value: " + $("input[name='rdoCategories']:checked").val());

Append item to container

The item will be added to the DOM and is available to jQuery immediately.

$('#rdoCategoriesContainer').append('<input type="radio" name="rdoCategories" value="tapes" />Audio tapes<br/>');
27Oct0

How to Disable Button on form submit in .NET

Posted by Michael Gaigg

This problem seems to be almost too obvious to be posted here but it took me quite some time to actually figure it out how to do it correctly - so I'd might just share it with you.

Disabling the submit button helps users comprehend that their action is in process and waiting for a response can be expected. It also prevents them from clicking the same action more than once which could lead to serious troubles (duplicate entries, application exceptions, etc.)

Problem

How do I disable a form submit button on a .NET page that does client-side validation?
The problem is that the button cannot simply be disabled because it would not be enabled again if the client-side validation prevents the form from being submitted.

Solution

.NET

<asp:Button runat="server" ID="btnSubmit" Text="Submit" OnClientClick="SubmitForm(this);" />

JavaScript:

function SubmitForm(source) {
ret = true;
if (typeof (Page_ClientValidate) == 'function') {
Page_ClientValidate();
ret = Page_IsValid;
}
if (ret) {
source.value = "Processing...";
source.disabled = true;
__doPostBack(source.name, "");
}
return ret;
}