First off, to enable sessions in node.js with Express, add the following lines to the app config call:

app.use(express.cookieParser());
app.use(express.session({ secret: "keyboard cat" }));

And that will just do it – super easy.

If you run into a 500 error “Cannot set property X of undefined” it means you placed those two lines below app.use(app.router). It is important that app.use(app.router) is BELOW in your configuration function.

Also, to make sure your session variables are available in jade templates (including layout), use dynamic helpers included with Express:

app.dynamicHelpers({
  session: function(req, res){
    return req.session;
  }
});

In your jade template, simply call session variable like any other variable:

p#id My session var: #{session.var_name}

To remove fields from documents in a collection use:

db.test.update({data:{$exists:true}},{$unset:{data:1}},{multi:1});

Or, if you want to add new fields, use set:

db.test.update({data:{$exists:false}},{$set:{data:"your value"}},{multi:1});

Set “multi” to 1 if you want to update/remove fields in all documents that match the criteria.

Another funny issue I ran into: apparently jquery can not find elements by ID (#) if the ID string starts with a hashtag (#). In my case, I was using IDs generated from twitter hashtags, and as you know hashtags start with #

So, using $(‘p##myhashtag’).html() did not work. What I could do, is to change the ID of the element and remove the # from the ID. But how do you do it with jade?

That’s when variable support in jade comes in handy! You can manipulate your data right in jade templates using regular javascript. Here’s a snippet that removes hashtag (first character in your string):

    - var st = hashtag
    - var len = st.length
    - var myst = st.substr(1,len)
    p(id=myst)

I was curious to see if it’s possible to create tabbed navigation and pass current URL parameter to jade from node.js.

It is in fact doable and fairly easy.

In your node.js server, make sure to pass the current URL variable to the your template:

app.get('/users', function(req, res){
  controller.getUsers( function(error, userData){
     res.render('users.jade',{ locals: {
   	users:userData,
   	currentURL:'/users/' 
        }
     });
  });
});

Then, in your jade template, use the conditionals to check for current URL:

div#nav
      ul
        li 
          if(currentURL == '/trends/')
            a(href='/trends/').current Trends
          else
            a(href='/trends/') Trends
        li
          if(currentURL == '/users/')
             a(href='/users/').current Users
          else
             a(href='/users/') Users
        li
          if(currentURL == '/seeds/')
             a(href='/seeds/').current Seeds 
          else
             a(href='/seeds/') Seeds

And here’s a bonus CSS to create nice tabs as your top nav:

#nav ul{text-align:left;border-bottom:1px solid #ccc; 
list-style-type:none;padding:10px 10px;}
#nav ul li{display:inline;}
#nav ul li a{font-weight:bold;border:1px solid #ccc; 
text-decoration:none;padding:10px 20px;
border-bottom:none;margin-right:5px;
margin-bottom:1px;background-color:#eee}
#nav ul li a.current{background-color:#fff;
border-bottom:1px solid #fff;}
#nav ul li a:hover{color:#000;background-color:#eee;}

And that should create a nice nav bar looking like this:

One cool thing about node.js is ability to pass data from server to client-side with just a couple of lines of code, if you use Express+Jade.

Here’s a quick example:

AS I was debugging my test node app, I noticed that every http request was sent as actual 2 requests:

– data request (came back with status 200)
– favicon.ico file request (came back with 400, when I hit twitter API)

To get rid of it, simply add an if statement around your http request

if (req.url != '/favicon.ico') {
// send your request
}


Also found a useful snippet in gist on this: https://gist.github.com/763822

Today I wanted to test out how to fetch data from one of the http APIs and save it to Mongo.

A quick example: get Twitter profile data for a given Twitter username.

In languages like PHP, we’d call curl and pass the URL. With node.js it’s actually really simple, we just call the GET method.

We are setting our request object that will call “GET” with our specified URL and wait to receive the response.

Request also has another method “on” that will listen for response data to come back (‘data’ event).

NOTE: It is not enough to just detect the ‘response’ event, as it looks like data coming back in “chunks”. I created a variable called “completeResponse” that concatenated all chunks into the final complete response (before I added that, my app would throw errors because of incomplete json that I tried running through JSON.parse()). Then wait for the ‘end’ event before actually saving the data into mongo.

Detailed info on http request and this issue

After you get your final parsed data object, it’s ready to be saved into mongo.

Working example can be found on github: https://github.com/ntanya/datacoll.git

(right now it’s all running on local machine)