Select all checkboxes
HTML
<form>
<input type="checkbox" name="select_all" /> selecionar tudo
<br />
1 <input type="checkbox" name="selects" />
2 <input type="checkbox" name="selects" />
3 <input type="checkbox" name="selects" />
</form>
JavaScript
$('document').ready( function(){
$('input[name=select_all]').on('click', function(){
$('input[name=selects]').attr('checked', 'checked');
});
});