如何检查节点快递应用程序中是否存在数据

Question

am working on a node / express app and currently trying to check if some session data exists or not.

To call the session data I'm currently using {{ if data['username'] }} which works fine. To user a conditional if the data exists the following seems to work:

{% if data['username'] %} do this {% endif %}

However I'm not sure how to do something if it DOESN'T exist. Such as

{% if data['username'] != '' %}

Any ideas appreciated! Thanks

Answer 1

I'm assuming you're using Nunjucks here based on the templating, and with that you can do:

{% if not data['username'] %}
{% endif %}

Answer 2

It depends on the templating language you're using. If it's Twig you can use not or empty

{% if not data['username'] or data['username'] is empty %}
Do this
{% endif %}