Ajax post request don't work with flask route - ajax

Question

I'm trying to build a 'like' button with ajax and flask,but when I try to get the string for the button to decide which button was clicked,my alert always return 'None'.
flask relevant part:
#bp.route('/<int:id>/post', methods=('GET', 'POST'))
#login_required
def show_post(id):
my_opinion=request.form.get("opinion")
my_post=get_post(id,False)
if request.method == 'POST':
opi = request.form.get("opinion")
if opi == 'Like':
update_like(id,my_post,g.user['id'])
my_opinion='like'
elif opi == 'Dislike':
update_dislike(id,my_post,g.user['id'])
my_opinion='dislike'
user_info=g.user['id']
user_new = get_db().execute(
'SELECT liked_posts,disliked_posts'
' FROM user u'
' WHERE id = ?',
(user_info,)
).fetchone()
return render_template('blog/show.html',post=my_post,user=user_new,my=my_opinion)
ajax part:
<script src="https://code.jquery.com/jquery-3.5.1.js"
integrity="sha256-QWo7LDvxbWT2tbbQ97B53yJnYU3WhH/C8ycbRAkjPDc="
crossorigin="anonymous"></script>
<script type="text/javascript">
$(document).on('submit','.opin',function(e)
{
e.preventDefault();
$.ajax({
type:'POST',
url:'/1/post?author=josh',
data:{
opinion:"check"
},
success:function()
{
const new_opinion = document.getElementsByClassName("opinion");
let special = "{{my}}";
alert(special);
const cssObj = window.getComputedStyle(new_opinion[0], null);
let bgColor = cssObj.getPropertyValue("background-color");
if (bgColor=='rgb(128, 128, 128)'){
bgColor="linear-gradient(144deg,#AF40FF, #5B42F3 50%,#00DDEB)";
}
else{
bgColor="gray"
}
new_opinion[0].style.background=bgColor;
}
})
});
</script>
This part alert 'None':
let special = "{{my}}";
alert(special);
I'm trying to get 'check' string into 'my' template parameter.