To get the site url in the js file we can have different ways but worked for is listed below.
You could avoid hardcoding the full path by setting a JS variable in the header of your template, before wp_head() is called, holding the template URL. Like:
<script type="text/javascript"> var templateUrl = '<?= get_bloginfo("template_url"); ?>'; </script>
and call in js file
$("#nav-shadow li").append('<img class="shadow" src="'+templateUrl+'/images/shadow.jpg"/>');
Source : http://stackoverflow.com/questions/5221630/wordpress-path-url-in-js-script-file Posted By AJJ