How to add onchange event in django-python

Codes with on change in category to subcategory..

Forms.py

from django import forms
from .models import BlogSubCategory
class BlogForm(forms.ModelForm):

 class Meta:
 model = BlogSubCategory
 fields = "__all__"
 widgets = {'category':forms.Select(attrs={'onchange':'fn_GetSubcategory()'})}

views.py

from django.shortcuts import render,HttpResponse
from django.core import serializers
from .models import Blog,BlogSubCategory,BlogCategory
# Create your views here.
def getsubcategorybycategory(request, pk):

 try:
     __Data = BlogSubCategory.objects.filter(category__id=pk)
    qu_json = serializers.serialize('json', __Data)
    return HttpResponse(qu_json, content_type='application/json')
except Exception as er:
    return HttpResponse(er, content_type='application/json')

Name.js

function fn_TestJSON(text) {
 if (typeof text == "string") {
 return false;
 }
 try {
 text = JSON.stringify(text)
 JSON.parse(text);
 return true;
 } catch (error) {
 console.log(error)
 return false;
 }
}
function fn_GetSubcategory() {
 __ID = $('#id_category').val()
 $.ajax({
 url: '/subcategory/' + __ID + '/',
 }).done(function(res) {
 if (fn_TestJSON(res)) {
 var objHTML = '<option value="0">select subcategory </opction>'
 if (fn_TestJSON(res)) {
 $.each(res, function() {
 objHTML += '<option value="' + this.pk+ '">' + this.fields.name + '</option>'
 })
 }
 $('#id_subcategory').empty().append(objHTML)
 }
 });
}

Urls.py

from blogs.views import getsubcategorybycategory
urlpatterns = [
 path('admin/', admin.site.urls),
 path('subcategory/<int:pk>/', getsubcategorybycategory, name='getsubcategorybycategory'),
]

Admin.py

from .forms import BlogForm
class BlogAdmin(admin.ModelAdmin):
 form = BlogForm
 class Media:
 js = (
 "js/jquery.js",
 "js/blog.js",
 )