How do I pass content from a template to a layout in Express?

Question

I have a basic Express server:

// server.js:
var Express = require('express');
app = Express.createServer();
app.configure(function(){
  app.set('views', Path.join(__dirname, 'views'));
  app.set('view engine', 'jade');
  app.set('view options');
});
app.get('/', function (request, response) {
  response.render('welcome', {
    locals: {some: 'Locals'}
  });
});

With a basic jade layout:

// views/layout.jade:
!!! 5
html(lang='en')
  head
    title= pageTitle
  body
    h1= pageTitle
    aside(id="sidebar")= sidebarContent
    #content
      #{body}

And a simple page:

# views/welcome.jade:
// How do I pass pageTitle and sidebarContent out to the layout from here?
p
  Welcome to my fine site!

(In Rails, this might be something like content_for or a simple instance variable.)

Answer 1

Using the tip above about dynamicHelpers, and the magic of closures, I found a fairly elegant solution that works without involving the request object. The trick is to wrap the page title variable in a closure that provides a get() and set() function around it, and make that wrapper object the result of the page_title dynamic helper.

Create a property.js:

exports.create = function () {
    var value = null;
    return {
        get: function () {
           return value;
        },
        set: function (new_value) {
           value = new_value;
        }
    };
}

So calling create() returns an object with a get() and set() method on it, that get and set the closure variable.

Then, in your app's setup code:

    var property = require("./property.js");
    app.dynamicHelpers ({
        page_title: function () {
         return property.create ();
        }
    });

Since the dynamic helper's value is the result of calling its function, in your view and template, the page_title variable will be the wrapper object with the get() and set() functions.

In your view, you can then say:

- page_title.set ("my specific page title");

And in your layout:

title= page_title.get()

To simplify this a bit further, adding this to property.js:

exports.creator = function () {
    return function () {
        return exports.create();
    };
}

Lets you simplify the dynamic helpers declaration block to this:

        var property = require("./property.js");
        app.dynamicHelpers ({
            page_title: property.creator()
        });

Answer 2

Express does not have a preconceived notion of "blocks" or whatever they call that in in rails, but you can use a combination of helpers() and dynamicHelpers() to achieve something similar http://expressjs.com/guide.html#app-helpers-obj-

Locals passed are available to both the layout and the page view though

Answer 3

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.

Answer 4

You can do that by using this little snippet.

prop.js:

var hash = {};
module.exports = function() {
    return {
        set: function(key, val) { hash[key] = val },
        get: function(key) { return hash[key] }
    };
};

server.js:

app.dynamicHelpers({ prop: require(__dirname + '/views/helpers/prop') });

---

View:

<% prop.set('foo', 'bar') %>

Layout:

<%= prop.get('foo') %>

Answer 5

Pass it in locals: {some: 'Locals', pageTitle: 'Welcome!'}

Answer 6

For Express 3 template agnostic, works well with express-partials

app.use (req, res, next)->
  req.locals = {} unless req.locals

  res.locals.content_for = (k, v = null)->
    if !v
      req.locals[k]
    else
      req.locals[k] = v

  next()