RebelBase: Adding JS Functionality to a Rails Application

Posted by jouissances on June 10, 2019

Learning JavaScript after spending so much time on Ruby is such a ride! I love spending time solving JS challenges on Codewars, but mini logic challenges are somehow different from implementing JS on a web app. This is my first time working with both Ruby and JS on a project, so I learned a lot!

1. Discovery

Initially, after reading the portfolio assessment requirements, I decided that I’m going to make these changes to my Rails app:

  • Render user’s clubs on Memberships index using JS
  • Allow user to click through the upcoming books list and read books list by clicking on ‘Next’ on the Book show page with AJAX
  • Render Discussion’s list of Comments with AJAX
  • Submit a Comment to a Discussion with AJAX
  • Construct Discussion as JS Model Object
  • Render the username of the user who posted the Comment with AJAX
  • Render Comment creation time with AJAX

As you can tell, a lot of AJAX is going to happen! Essentially, AJAX is a technique used to create asynchronous web-apps. Asynchronous means that while we send a method call to the server, our web page is not blocked / frozen while loading the results. We can even interact with other elements on the page while waiting for the call to finish retrieving our results! But for our small virtual book club app, the time needed to retrieve the results is very short, so we won’t need to do that.

2. Strategy

A strategy that I employed here is to firstly serialize all my models using Active Model Serializer. AMS is a gem that easily lets me convert my data into JSON. I didn’t need to serialize all the models, as I was planning to implement AJAX for only the following models: Memberships, Books, Discussions, and Comments; but I did it anyways, just in case. After serializing, I edited my controllers to allow me to access the views as .json, in addition to .html. This was fun. I use the JSONView Chrome Extension to view my JSON data in a neat format, and to expand or collapse any data I need). AMS also allows me to specify any associations between my models.

I used the same associations as the ones I used for my schema. I realised that later on, I needed to modify this slightly — more on that later! After confirming that the data and associations were rendering perfectly, I went on to coding the JS. This is where the hard part begins.

3. Design

I didn’t focus much on visual design here, as this project mainly serves as a coding challenge for me. I did fix some CSS weirdness, but that was it.

4. Architecture

Rails’ architecture allowed me to separate my JS file according to the views and models that I’m focusing on. To implement AJAX on the discussion#index page, I only need to code my JS in discussion.js (which I changed from— CoffeeScript is something that I’ll learn in the future, along with many other things).

In terms of the views structure, I separated Discussions views from those of Book‘s. What this means is that previously, you can look at a book’s discussions from the individual book’s book#show page, but I realised that this also means that the AJAX calls for discussion#index will need to be placed in books.js (as the Discussions are rendered via the Books controller). I then decided to move the Discussions views to its own rightful folder, which feels cleaner and more easily manageable.

5. Development

Longest part of the process. I had to watch many Learn videos to do this. I signed up for Rails+JS study groups, but they were conducted during my work hours and unfortunately I couldn’t attend them, so I resorted to the recordings instead. I find Brad’s study session recording really helpful! He even posted the code in his GitHub repository.

One of the bugs that I realised early on was that my AJAX calls were firing multiple times. I found out that this was because I have specified the following in my application.js:

//= require jquery
//= require rails-ujs
//= require jquery-ujs
//= require_tree .
//= require popper
//= require bootstrap
//= require typed

Do you see it? I had called on multiple jQuery files, which resulted in each AJAX request being fired twice. I deleted the jquery-ujs line, and everything was restored beautifully (no more double vision!).

Another bug happened when I had to click on a link twice before I see the results being appended onto my view. This was because I had accidentally nested a click function within another click function, which was a mess. This has been corrected.

One of my biggest learning points for this project was in learning to use $.ajax() and $.getJSON(). I used both for different parts of the project, just to practice more with both styles. Personally, I prefer the latter, as it is a shorthand for $.ajax() — it has already specified the parameter for the output, which is in JSON, and it automatically transforms my JSON output into an Object. Yum. I find $.getJSON() to be more configurable as well, as I can easily specify, configure, and see which URL I’m retrieving my request from.

I also learned to manipulate the serialised JSON data into giving me specific key-value pairs. In the discussion_serializer.rb file, for example, I added a custom method:

class DiscussionSerializer < ActiveModel::Serializer
  attributes :id, :title, :body, :book_quote, :comments_with_user

  # include created_at and updated_at

  belongs_to :book
  belongs_to :user

  # has_many :comments

  def comments_with_user
    array = [] do |comment|
      hash = {}
      hash['id'] =
      hash['body'] = comment.body
      hash['created_at'] = comment.created_at
      hash['updated_at'] = comment.updated_at
      hash['discussion_id'] =
      hash['username'] = comment.user.username
      array << hash


To render each comment’s username, I had to be able to access the comment’s user_id from my Discussion JS Object. What I realised was that my Discussion JS Object didn’t have access to the nested comment’s user_id, discussion_id, as AMS only went one-level nest-deep.

However, I was able to see the user_id when I navigate straight to the Comments.

So I needed to make my discussion_serializer.rb serve me my JSON as I like it, which was what the custom method comments_with_user is doing. I was able to construct a new key-value pair for my Discussions Object, retrieve the information I needed, and access it via discussions.json.

After I have my comments_with_user data, I didn’t need AMS to give me my original comments (without user) list, and so I commented the line has_many :comments (line 9) from discussion_serializer.rb.

6. Deployment

I checked out a new git branch to develop the JS features, and submitted my own pull and merge requests. For the live deployment, I will continue to use Heroku for the time being, but I look forward to learning more about server and hosting, especially with AWS EC2, which I’ve been hearing a lot about!

Thank you for reading!