Use of $s $x $v

$x

$x is used to find the control on the DOM meaning looking for any item available on DOM.
If the control is found then it returns the dom of the Item else false.

Syntax 
$x('PAGE_ITEM');

$v

$v is used to get the value from the item.
Syntax 
$v('PAGE_ITEM');

$s

$s is used to set the values in Item.
Syntax 
$s('PAGE_ITEM','New value');