Express & jade (node.js) - variable is not defined error when checking for existence

Question

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)".

Community · Accepted Answer · 2017-05-23 11:45:58Z

13

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}

edited May 23, 2017 at 11:45

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answered Sep 3, 2012 at 19:57

Jade

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Comments

PitaJ · Accepted Answer · 2012-05-22 20:25:42Z

3

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

try

if(typeof obj != 'undefined')

edited May 22, 2012 at 20:25

answered May 22, 2012 at 20:19

PitaJ

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1 Comment

uorbe001 Over a year ago

This does work, thanks!. I still think the simple check should work though, it is much cleaner :-(.

Tracker1 · Accepted Answer · 2013-05-14 23:06:51Z

1

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.

answered May 14, 2013 at 23:06

Tracker1

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