App.js

// app/assets/javascripts/App.js
class App {
  static initJobShow() {
    $(document).ready(function(){
      let user_id = $(".user-id").data("id")
      let job_id  = $(".job-id").data("id")

      $.get(`/users/${user_id}/jobs/${job_id}.json`, function(data) {
        let job = new Job(date, user_id)

        $('#foo').append(JobView.renderJobShow(job))
      })
    })
  }

  static initJobIndex() {
    // ...
  }
}

// app/assets/javascripts/job/view/JobView.js
class JobView {
  static renderJobShow(job) {
    $('<div>', {}, [ renderJobTitle(job), ... ])
  }

  static renderJobTitle(job) { ... }
  static renderJobAppliedBtn(job) { ... }
}


// ///// app/views/layout/application.html.erb /////
//
// ...
//
// = javascript_tag 'App.js' # ^ our `App` class above

// ///// app/views/jobs/show.html.erb /////
//
// ...
//
// <script type='text/javascript'>
//   App.initJobShow()
// </script>