expressJs default value of title variable declaration - node.js

Question

Where does express get the default value for its title variable. My index.jade looks like the following:
h1= title
p Welcome to #{title}
I don't quite understand where the title variable is set.

Answer 1

In your routes/index.js you will be saying
res.render('index', { title: 'Express' });
So here it will find views/index.jade put value of title variable as 'Express'.
You can say in your jade
p Welcome to #{title} from #{name}
and while renderring
res.render('index', { title: 'Express' ,name: 'myName'});
it will be converted in Welcome to Express from myName.

Answer 2

In express, the template (.jade for example) has access to
anything in app.locals which are basically global variables
anything in res.locals which are tied to the request/response cycle of the current request
anything passed to it via res.render() which will have typically been determined in your request route handler
Just to expand on this, here is an example that should demonstrate:
app.js:
var express = require('express');
var routes = require('./routes');
var http = require('http');
var path = require('path');
var app = express();
//set a global variable that will be available to anything in app scope
app.locals.globalVar = "GLOBAL";
// all environments
app.set('port', process.env.PORT || 3000);
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');
app.use(express.urlencoded());
app.use(express.methodOverride());
//register a middleware that will set a local variable on the response
app.use(function (req, res, next) {
res.locals.resLocalVar = new Date();
next();
});
app.use(app.router);
app.get('/', routes.index);
app.get('/:id', routes.index);
http.createServer(app).listen(app.get('port'), function(){
console.log('Express server listening on port ' + app.get('port'));
});
index.js:
exports.index = function (req, res) {
var id = req.params.id || "Nothing"
res.render('index', { renderVar: id });
};
index.jade:
extends layout
block content
p I am a global variable with value: #{globalVar}
p I am scoped to the current request/response with value: #{resLocalVar}
p I am only set on the call to render() in index.js and my value is: #{renderVar}
When you visit http://localhost:3000/[some value] you will see the values of app.locals.globalVar, res.locals.resLocalVar, and also the value of renderVar that's defined in the call to res.render() in index.js.

Answer 3

You can set view variables at the app level, the response level, and/or at the time of render.