javascript - jquery select all checkboxes

Question

I have a series of checkboxes that are loaded 100 at a time via ajax.

I need this jquery to allow me to have a button when pushed check all on screen. If more are loaded, and the button is pressed, to perhaps toggle all off, then pressed again toggle all back on.

This is what i have, obviously its not working for me.

$(function () {
 $('#selectall').click(function () {
  $('#friendslist').find(':checkbox').attr('checked', this.checked);
 });
});

The button is #selectall, the check boxes are class .tf, and they all reside in a parent div called #check, inside a div called #friend, inside a div called #friendslist

Example:

<div id='friendslist'>
    <div id='friend'>
        <div id='check'>
            <input type='checkbox' class='tf' name='hurr' value='durr1'>
        </div>
    </div>
    <div id='friend'>
        <div id='check'>
            <input type='checkbox' class='tf' name='hurr' value='durr2'>
        </div>
    </div>
    <div id='friend'>
        <div id='check'>
            <input type='checkbox' class='tf' name='hurr' value='durr3'>
        </div>
    </div>
</div>

<input type='button' id='selectall' value="Select All">

Answer 1

I know I'm revisiting an old thread, but this page shows up as one of the top results in Google when this question is asked. I am revisiting this because in jQuery 1.6 and above, prop() should be used for "checked" status instead of attr() with true or false being passed. More info here.

For example, Henrick's code should now be:

$(function () {
    $('#selectall').toggle(
        function() {
            $('#friendslist .tf').prop('checked', true);
        },
        function() {
            $('#friendslist .tf').prop('checked', false);
        }
    );
});