How to retrieve checkboxes values in jQuery

Here's one that works (see the example):

 function updateTextArea() {         
     var allVals = [];
     $('#c_b :checked').each(function() {
       allVals.push($(this).val());
     });
     $('#t').val(allVals);
  }
 $(function() {
   $('#c_b input').click(updateTextArea);
   updateTextArea();
 });

Update

Some number of months later another question was asked in regards to how to keep the above working if the ID changes. Well, the solution boils down to mapping the updateTextArea function into something generic that uses CSS classes, and to use the live function to monitor the DOM for those changes.

Your question is quite vague but I think this is what you need:

$(function() { 
    $('input[type="checkbox"]').bind('click',function() {
        if($(this).is(':checked')) {
            $('#some_textarea').html($(this).val());
         }
   });
});

Edit: Oh, okay.. there you go... You didn't have the HTML up before. Anyways, yeah, I thought you meant to put the value in a textarea when it gets clicked. If you want the checked checkboxes' values to be put into the textarea (maybe with a nice comma-seperation) on page load it would be as simple as:

$(function() { 
    $('#c_b input[type="checkbox"]:checked').each(function() { 
        $('#t').append(', '+$(this).val());
    });
});

Edit 2 As people have done, you can also do this to shortcut the lengthy selector I wrote:

$('#c_b :checkbox:checked').each(function() {
    $('#t').append(', '+$(this).val());
});

... I totally forgot about that shortcut. ;)

The following may be useful since I got here looking for a slightly different solution. My script needed to automatically loop through input elements and had to return their values (for jQuery.post() function), the problem was with checkboxes returning their values regardless of checked status. This was my solution:

jQuery.fn.input_val = function(){

    if(jQuery(this).is("input[type=checkbox]")) {
        if(jQuery(this).is(":checked")) {
            return jQuery(this).val();
        } else {
            return false;
        }
    } else {
        return jQuery(this).val();
    }
};

Usage:

jQuery(".element").input_val();

If the given input field is a checkbox, the input_val function only returns a value if its checked. For all other elements, the value is returned regardless of checked status.

Here's an alternative in case you need to save the value to a variable:

var _t = $('#c_b :checkbox:checked').map(function() {
    return $(this).val();
});
$('#t').append(_t.join(','));

(map() returns an array, which I find handier than the text in textarea).

$(document).ready(function() {
  $(':checkbox').click(function() {
    var cObj = $(this);
    var cVal = cObj.val();
    var tObj = $('#t');
    var tVal = tObj.val();
    if (cObj.attr("checked")) {
      tVal = tVal + "," + cVal;
      $('#t').attr("value", tVal);
    } else {
      //TODO remove unchecked value.
    }
  });
});

$("#t").text($("#cb").find(":checked").val())

Anyway, you probably need something like this:

 var val = $('#c_b :checkbox').is(':checked').val();
 $('#t').val( val );

This will get the value of the first checked checkbox on the page and insert that in the textarea with id='textarea'.

Note that in your example code you should put the checkboxes in a form.

If you want to insert the value of any checkbox immediately as it is being checked then this should work for you:

$(":checkbox").click(function(){
  $("#id").text(this.value)
})

I have had a similar problem and this is how i solved it using the examples above:

 $(".ms-drop").click(function () {
        $(function showSelectedValues() {
            alert($(".ms-drop input[type=checkbox]:checked").map(
               function () { return this.value; }).get().join(","));
        });
    });