Jade - Template Engine: How to check if a variable exists
node.jsPugExpressnode.js Problem Overview
I'm currently using Jade on a new project. I want to render a page and check if a certain variable is available.
app.js:
app.get('/register', function(req, res){
res.render('register', {
locals: {
title: 'Register',
text: 'Register as a user.',
}
});
});
register.jade:
- if (username)
p= username
- else
p No Username!
I always get the following error:
username is not defined
Any ideas on how I can fix this?
node.js Solutions
Solution 1 - node.js
This should work:
- if (typeof(username) !== 'undefined'){
//-do something
-}
Solution 2 - node.js
Simpler than @Chetan's method if you don't mind testing for falsy values instead of undefined values:
if locals.username
p= username
else
p No Username!
This works because the somewhat ironically named locals is the root object for the template.
Solution 3 - node.js
if 'username' in this
p=username
This works because res.locals is the root object in the template.
Solution 4 - node.js
If you know in advance you want a particular variable available, but not always used, I've started adding a "default" value to the helpers object.
app.helpers({ username: false });
This way, you can still do if (username) { without a catastrophic failure. :)
Solution 5 - node.js
Even simpler with pug, the successor to jade
if msg
p= msg
Solution 6 - node.js
Shouldn't 'username' be included in the locals object?
Solution 7 - node.js
Created a middleware to have the method isDefined available everywhere in my views:
module.exports = (req, res, next) => {
res.locals.isDefined = (variable) => {
return typeof(variable) !== 'undefined'
};
next();
};