I have this situation. I have some bookcovers on my static files on Django. The jpg files names are the isbn of each book. 
I am building img tags on Javascript and would like to incluide these images to change dinamically. I got each book's isbn already in a variable called "isbn". I am assigning it in this way:
var src = "{% static 'img/" + isbn + ".jpg' %}";, and then adding it to the img element. However, the src is been taking as follows: <img id="book-card1img" src="/static/img/%22%20%2B%20isbn%20%2B%20%22.jpg" class="card-img-top">.
Is something I am doing wrong?