express node.js partials pug templates

Using javascript code in Jade views – if(variable) shows undefined instead of passing

So this is a recurring issue I have and haven’t found another example on SO so here goes:

When rendering Jade templates I get 'variableName' undefined even when using -if(variableName) in the template.

Example (I’m using this as a partial for ‘info’ flash messages):

- if(info.length){
li= info

This returns ‘info’ is not defined instead of not rendering anything when there isn’t a flash/info message. Does anyone know what I’m doing wrong?

I’m aware of the typeof(variable) != 'undefined option as mentioned. If I wanted to do something like -if (typeof(req.session.user) != 'undefined') I would have to do 3 nested `if (typeof(req) != ‘undefined’. Is this my only option?