mean menu custom width call in jquery

Question

js every thing works fine but i have a problem ... My website have two navigation on different pages can any one tell me how to call the meanscreenWidth by custom.js file i have used below code but no effect..

<script type="text/javascript">
    jQuery(document).ready(function () {

            if('meanScreenWidth: "480"'){
            jQuery('header .topFront nav').meanmenu();
            }

            else if{
                         ('meanScreenWidth: "767"'){
            jQuery('header nav').meanmenu();
                         }
        });
</script>  

js every thing works fine but i have a problem ... My website have two navigation on different pages can any one tell me how to call the meanscreenWidth by custom.js file i have used below code but no effect..

<script type="text/javascript">
    jQuery(document).ready(function () {

            if('meanScreenWidth: "480"'){
            jQuery('header .topFront nav').meanmenu();
            }

            else if{
                         ('meanScreenWidth: "767"'){
            jQuery('header nav').meanmenu();
                         }
        });
</script>