absolutize_path.py

from django import template
from django.conf import settings

register = template.Library()


@register.simple_tag(takes_context=True)
def absolutize_path(context, *args):
    relative_url = ''.join(args)
    absolute_paths = context.get('absolute_paths', False)
    if absolute_paths:
        if relative_url.startswith('/'):
            relative_url = relative_url[1:]
        return '{}/{}'.format(settings.APPS_DIR, relative_url)
    else:
        return relative_url

Use it in templates as:

{% load absolutize_path %}
...
<script src="{% absolutize_path STATIC_URL 'js/project.js' %}"></script>

if you pass absolute_paths=True in the context the output will be the absolute file system path as /app/app_name/static/js/project.js, else you will get the standard /static/js/project.js