Auto-select next field as the user (de-)fills them. Useful for three phone number fields.

Auto-select Fields

var $phone1 = $('input#phone1');
var $phone2 = $('input#phone2');
var $phone3 = $('input#phone3');

$phone1.change(function() {  
 if ($phone1.val().length == 3) // if they've typed 3 characters
   $phone2.focus(); // select the next field
});

$phone2.change(function() {  
 if ($phone2.val().length == 3) // if they've typed 3 characters
   $phone3.focus(); // select the next field
 else if ($phone2.val().length == 0) // if they backspace to 0 characters
   $phone1.focus(); // select the previous field
});

$phone3.change(function() {  
 if ($phone3.val().length == 0) // if they backspace to 0 characters
   $phone2.focus(); // select the previous field
});