Question

I can’t check checkboxes on second attempt(i can check then uncheck, but after this no effect)

See http://jsfiddle.net/SM5qU/1/

Attributes set to checked=”checked” but no visual effect.
I am using MacOS and tested in Chrome and Firefox

HTML

<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />
<input type="checkbox" />

<button id="check">Check</button>
<button id="uncheck">Uncheck</button>

JS

$('#check').click(function() {
    $(':checkbox').attr('checked', true)
})

$('#uncheck').click(function() {
    $(':checkbox').attr('checked', false)
})

Answer 1

use .prop() in your case:

$(':checkbox').prop('checked', true);

$(':checkbox').prop('checked', false);