Rails Ajax Examples (Without jQuery)

Posted on October 26, 2019 - 3 Minute Read

Introduction

Rails ships with turbolinks which:

automatically fetches the page, swaps in its <body>, and merges its <head>, all without incurring the cost of a full page load.

This creates a reactive, fast application. However, there are times when turbolinks is not enough, and you'll want to roll your own AJAX solutions.

Blueprint

Below is a generic blueprint to follow when implementing AJAX on the create action of a model in a Rails application.

1: Controller

Create a respond_to block and make sure to pass format.js in the block. This will automatically render a corresponding create.js.erb file. This file needs to be manually created in the corresponding views directory.

  def create
    @your_model = YourModel.create(your_model_params)
      respond_to do |format|
          if  @your_model.save
              # This will run the code in `app/views/your_model/create.js.erb`.
              format.js
          else
              # This will run the code in `app/views/your_model/create.js.erb`.
              format.js
          end
      end
  end

2: Form

Make sure your form does not use local: true. Otherwise, the form will not submit remotely.

<%= form_with model:@your_model do |f| %>
  ...
<% end  %>

3: Create View

Handle errors and successful model creations with Javascript in your corresponding app/views/your_model/create.js.erb file. Note that any ruby code will get evaluated first. This means that you still have access helpful Rails layout and rendering methods, such as Partials.

# app/views/your_model/create.js.erb
<% if @your_model.errors.any? %>
  # Handle errors
<% else %>
  # Handle save
<% end %>

Example 1: Dynamically Add a New Comment to a List of Comments with Ajax

In this scenario you want to post a new comment to a list of existing comments asynchronously.

Add a comment via AJAX

Create View

<% if @comment.errors.any? %>
    <%# This removes any error messages that were previously generated. %>
    document.querySelector('#error_explanation') ? document.querySelector('#error_explanation').remove() : null ;
    <%# This selects the `<form>` in and dynamically injects the `app/views/shared/_validation-messages.html.erb` partial. %>
    document.querySelector('#comments-form').insertAdjacentHTML('afterbegin', '<%= escape_javascript(render "shared/validation-messages", object: @comment) %>');
<% else %>
    <%# This removes any error messages that were previously generated. %>
    document.querySelector('#error_explanation') ? document.querySelector('#error_explanation').remove() : null ;
    <%# This selects `<div id="comments">` and dynamically injects the `app/views/comments/_comment.html.erb` partial. %>
    document.querySelector('#comments').insertAdjacentHTML('afterbegin', '<%= escape_javascript(render @comment) %>') ;
    <%# This selects the `<form>` and resets the text area. %>
    document.querySelector('#comments-form').reset();
<% end %>

Example 2: Dynamically Add a New Author to a Select List of Existing Authors

In this scenario you want to create a new author while adding or editing an existing post that relies on a relationship with an author.

Add an author via AJAX

Create View

<% if @author.errors.any? %>
    <%# This removes any error messages that were previously generated. %>
    document.querySelector('#error_explanation') ? document.querySelector('#error_explanation').remove() : null ;
    <%# This selects the new author `<form>` and dynamically injects the `app/views/shared/_validation-messages.html.erb` partial. %>
    document.querySelector('#author_form').insertAdjacentHTML('afterbegin', '<%= escape_javascript(render "shared/validation-messages", object: @author) %>');
<% else %>
    <%# This removes any error messages that were previously generated. %>
    document.querySelector('#error_explanation') ? document.querySelector('#error_explanation').remove() : null ;
    <%# This searches for the currently selected author and unselects them. %>
    document.querySelector("select#post_author_id option[selected='selected']") ? document.querySelector("select#post_author_id option[selected='selected']").removeAttribute('selected') : null ;
    <%# This dynamically adds the newly created author into the author select list, and sets them to be selected. %>
    document.querySelector('select#post_author_id').insertAdjacentHTML('afterbegin', '<option value="<%= @author.id %>" selected="selected" ><%= @author.formatted_name %></option>') ;
    <%# This selects the new author `<form>` and resets the text fields. %>
    document.querySelector('#author_form').reset();
<% end %>
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