I'm getting a pretty dumb error on a extremely simple express app. I am using jade as the view engine, I'm saying this just in case it is related to the problem.

I'm trying to check if a variable is defined in order to render one thing or another, but simply checking for that variable triggers a "variable is not defined" Error. This is not the behaviour I'd expect, so I'm wondering if I'm doing something wrong. This is the view code I'm using:

h1= title
- if (user)
    p Welcome to #{title}, #{user.username}
- else 
    p Welcome to #{title}

What is the right way to do this? There must be a way to check for variables on the views. :-/

EDIT: Forgot to say on what line the error is triggered, it is triggered on the second line "- if (user)".

I'm getting a pretty dumb error on a extremely simple express app. I am using jade as the view engine, I'm saying this just in case it is related to the problem.

I'm trying to check if a variable is defined in order to render one thing or another, but simply checking for that variable triggers a "variable is not defined" Error. This is not the behaviour I'd expect, so I'm wondering if I'm doing something wrong. This is the view code I'm using:

h1= title
- if (user)
    p Welcome to #{title}, #{user.username}
- else 
    p Welcome to #{title}

What is the right way to do this? There must be a way to check for variables on the views. :-/

EDIT: Forgot to say on what line the error is triggered, it is triggered on the second line "- if (user)".

• javascript
• node.js
• view
• pug

3 Answers 3

As is mentioned in another answer the Public API section of the Jade documentation says that the locals variable is how data is passed to a Jade template. On a lark I prepended my variables in the jade template with locals. This correctly bypassed the error.

So the following Jade template should resolve your error:

h1= title
- if (locals.user)
    p Welcome to #{title}, #{user.username}
- else 
    p Welcome to #{title}

You didn't enclose p Welcome to #{title}; #{user.username} in quotes

try

if(typeof obj != 'undefined')

layout.jade

# the following function is a safe getter/setter for locals
- function pagevar(key, value) { var undef; return (value===undef) ? locals[key] || null : locals[key] = value; }
block config
  #intended as a non-rendered block so that locals can be overridden.
  # put your defaults here... - use append in the child view
!!!
html
  head
    title=pagevar('title')
    meta(name='description',content=pagevar('description'))
...

page.jade

append config
  - locals.title = 'override';
  - locals.description = 'override 2';
  - pagevars('somekey', 'some value');
...

Easy peazy.