INSTALLED_APPS = [
  'django.contrib.admin',
  'django.contrib.auth',
  'django.contrib.contenttypes',
  'django.contrib.sessions',
  'django.contrib.messages',
  'django.contrib.staticfiles',
  'app01.apps.App01Config', # 自定义APP注册
]

from django.contrib import messages

def abc(request):
  messages.success(request, "哈哈哈")

{% if messages %}
  <script>
    {% for msg in messages %}
      alert('{{ msg.message }}');
    {% endfor %}
  </script>
{% endif %}