Check if checkbox is checked with jQuery

$('#' + id).is(":checked")

That gets if the checkbox is checked.

For an array of checkboxes with the same name you can get the list of checked ones by:

var $boxes = $('input[name=thename]:checked');

Then to loop through them and see what's checked you can do:

$boxes.each(function(){    // Do stuff here with this});

To find how many are checked you can do:

$boxes.length;

IDs must be unique in your document, meaning that you shouldn't do this:

<input type="checkbox" name="chk[]" id="chk[]" value="Apples" /><input type="checkbox" name="chk[]" id="chk[]" value="Bananas" />

Instead, drop the ID, and then select them by name, or by a containing element:

<fieldset id="checkArray">    <input type="checkbox" name="chk[]" value="Apples" />    <input type="checkbox" name="chk[]" value="Bananas" /></fieldset>

And now the jQuery:

var atLeastOneIsChecked = $('#checkArray:checkbox:checked').length > 0;//there should be no space between identifier and selector// or, without the container:var atLeastOneIsChecked = $('input[name="chk[]"]:checked').length > 0;

$('#checkbox').is(':checked'); 

The above code returns true if the checkbox is checked or false if not.