Data Manipulation

It didn’t take long before the need to adjust the data on the server sent by the Habit App needed to be adjusted.

For whatever reason, ok there’s a good reason and it’s because I wasn’t careful in sending data to the server, the habit data on the server I was working with was overwritten. The feature I’m working on is to populate the Habits if the Settings for URL and Username are set and there aren’t any configured. We’ll get to that in a minute though.

In the meantime whipping up some Node + Express + Jade templates was surprisingly very fun…

Express Frontend

There’s some additional setup to get Express ready for rendering templates. First, install Jade with:

npm install --save jade

Next, edit app.js and add the following toward the top of the file, somewhere after the var app = express(); statement:

app.set('view engine', 'jade');

This will tell Express that the app is using Jade for it’s template engine. Next, create a new views directory to hold our upcoming templates.

Before moving on, install the PouchDB Upsert plugin with:

npm install --save pouchdb-upsert

Then import the module in app.js after the PouchDB import:


Awesome, the app is ready to roll back documents to previous revisions and use cool cool templates.

New Routes

The first new route is actually a re-do of the / index route. Replace the static file serving app.get(‘/’, function(req, res){}); route with:

// GET /
// Return a simple welcome message.
app.get('/', function(req, res) {
  db.allDocs(function(error, docs) {
    res.render('index', {habits: docs, title: 'Habits'});

The new index route uses the PouchDB allDocs method to get all the the docs, or at least an array of their IDs which can then be used to get the actual JSON documents.

Next, add a route to GET /users/:username:

// GET /users/:username
app.get('/users/:username', function(req, res) {
  db.get(req.params.username, {rev: req.query.rev, revs: true}, function(error, doc) {
    if (error) {
      res.status(error.status).render('error', {error: error});

    res.render('user', {user: doc});

This route will get actual documents based on the :username request parameter.

The last new route is for rolling back documents to earlier revisions:

// GET /users/rollback/:username
app.get('/users/rollback/:username', function(req, res) {
  // Get the revision from the query string.
  db.get(req.params.username, {rev: req.query.rev}, function(error, oldDoc) {
    if (error) {
      res.status(200).render('error', {error: error});

    db.upsert(oldDoc._id, function(doc) {
      doc.habits = oldDoc.habits || [];
      return doc;
    }).then((result) => {
      // success!
      res.redirect('/users/' + req.params.username);
    }).catch(function (err) {
      // error (not a 404 or 409)

This route will lookup a :usernme and if found use the upsert method, from the PouchDB Upsert plugin, to set the doc’s attributes to the same as the revision passed via the request query string. Upsert is great because it takes care of any update conflicts. Not 100% sure why, but while developing this method I kept getting a bunch of conflicts… upsert to the rescue.

Jade Templates

The Jade template engine is one of the most concise ways of writing HTML that I have ever used. I was totally surprised how fun it was to code up some small pages using Jade. It does kind of remind me of HAML, but I never did use that.

In the new route statements above notice the res.render() statements at the end. The render method points to a template in the views directory. As you can imagine we have some new files to create.

First, create a views/layout.jade file:

doctype html
    title The Hoick Habit Server | #{title}

    link(href="/assets/css/main.css", rel="stylesheet", type='text/css')
    link(href='|Noto+Serif|Dekko', rel='stylesheet', type='text/css')
              a(href='/') Home
              a(href='/habits') API

        block content

This file can then be included via the Jade extends method inside the rest of the templates. So great to not have to repeat navigation elements in each template.

Now, create the views/index.jade file:

extends ./layout.jade  

block content
  h1 Welcome to The Hoick Habit Server
  h4 There is a JSON API.

  p See the <a href="/help">Help</a> page for more details.

  h3 Current Users:
    each habit in habits.rows

This template is pretty simple. It takes the habits object passed into the res.render method and loops over the habits.rows array returned by PouchDB.

Now for the big one. Create the views/user.jade template:

extends ./layout.jade  

block content
  h3 Username: #{user.username}

  h3 Habits

  if user.habits && user.habits.length > 0
      each habit in user.habits
          h4 Days:
            each day in habit.days
              li #[strong dayId:] #{day.dayId}
                | #[strong created_at:] #{day.created_at}
                | #[strong checked:] #{day.checked}

          h4 Reminder: #{habit.reminder}

    p No habits at this time...


  h3 Current Revision
  p= user._rev
  a(href='/users/rollback/#{user.username}?rev=#{user._rev}') Use This Revision?


  h3 Revisions
    each rev, idx in user._revisions.ids.reverse()
        | #[p #{idx + 1}: #[a(href='/users/#{user.username}?rev=#{idx + 1}-#{rev}') #{rev}]]

This template lists each Habit in habits, then loops over the Days array for each Habit. Notice that back in the get(‘/users/:username’) route that the PouchDB get method used the req.query.rev attribute, if there was one. Using this to get the document out of PouchDB will return the document at that revision. This is a great feature of PouchDB (and CouchDB for that matter). It’s been a life saver for me at times…

At the bottom of the template the revisions for the document are looped over and links are created for each previous revision.

Lastly, there is a little views/error.jade to have something a little more friendly to say if PouchDB doesn’t return a document, or there’s some other type of error:

extends ./layout.jade  

block content
  h1 Houston You Have a Problem

  h3 A #{error.status} error has occurred.

    strong Error Details:
    em name: #{}
    em message: #{error.message}
    em reason: #{error.reason}


Like I said, I hadn’t planned on making a front-end to The Hoick Habit Server, but once you get started manipulating data via curl get’s old fast.

Whipping up this simple web app was actually a lot of fun. I think getting to use Jade for a project was a lot of the fun because of how concise it allows you to write HTML.

Party On!