You don’t need javascript, just change the class using the get_theme_mod variable e.g.
<?php
$layout = get_theme_mod('embee_layout_section_options[site_layout]', '3');
$class="";
if($layout == '1') {
$class="this";
} elseif($layout == '2') {
$class="that";
}
?>
<div class="<?php echo $class; ?>">
// stuff
</div>
Put that in your template file e.g. page.php and the live customizer will pick it up
Then creates the classes e.g.
.this {
float:left;
}
.that {
float:right;
}
I have built some massive complex stuff in the customizer and never had to add javascript, it’s all done through the template files and get_theme_mod