jdsutherland
Modern Front-End Development for Rails: B7 pg 164 server JSON ids are numbers causing javascript Array#includes to always return false
After completing the section Using Data in Stimulus (ends pg 167), I noticed something wrong with Ajax updates. After running the rake task to sell out concerts, things looked fine on initial browser load:
but after Ajax it would change from “Sold Out” to “0 Tickets Remaining”:
The data attributes looked like this:
So concertSoldOutValue was suspiciously being set to false. The issue is that Array#includes is called with a string on an array of numbers (always false):
concertElement.dataset.concertSoldOutValue = soldOutConcertIds.includes(
concertElement.dataset.concertIdValue
)
typeof soldOutConcertIds[0]: number
The ids coming from the server JSON are numbers. One solution is to convert the ids to a string:
class SoldOutConcertsController < ApplicationController
def show
concerts = Concert.includes(:venue, gigs: :band).all
sold_out_concert_ids = concerts
.select(&:sold_out?)
.map(&:id)
.map(&:to_s)
render(json: {sold_out_concert_ids: sold_out_concert_ids})
end
end
Perhaps TypeScript could be leveraged to prevent this kind of bug?
First Post!
noelrappin
Author of Modern Front-End Development for Rails
This is a really great catch, I’ll fix it in the next update.
Popular Pragmatic Bookshelf topics
Working through the steps (checking that the Info,plist matches exactly), run the demo game and what appears is grey but does not fill th...
New
Hi everyone!
There is an error on the page 71 in the book “Programming machine learning from coding to depp learning” P. Perrotta. You c...
New
Title: Hands-On Rust (Chapter 11: prefab)
Just played a couple of amulet-less games. With a bit of debugging, I believe that your can_p...
New
Hi Jamis,
I think there’s an issue with a test on chapter 6. I own the ebook, version P1.0 Feb. 2019.
This test doesn’t pass for me:
...
New
In case this helps anyone, I’ve had issues setting up the rails source code. Here were the solutions:
In Gemfile, change
gem 'rails'
t...
New
The book has the same “Problem space/Solution space” diagram on page 18 as is on page 17. The correct Problem/Solution space diagrams ar...
New
I ran this command after installing the sample application:
$ cards add do something --owner Brian
And got a file not found error:
Fil...
New
The allprojects block listed on page 245 produces the following error when syncing gradle:
“org.gradle.api.GradleScriptException: A prob...
New
Getting an error when installing the dependencies at the start of this chapter:
could not compile dependency :exla, "mix compile" failed...
New
@mfazio23
Android Studio will not accept anything I do when trying to use the Transformations class, as described on pp. 140-141. Googl...
New
Other popular topics
I’ve been hearing quite a lot of comments relating to the sound of a keyboard, with one of the most desirable of these called ‘thock’, he...
New
Thanks to @foxtrottwist’s and @Tomas’s posts in this thread: Poll: Which code editor do you use? I bought Onivim! :nerd_face:
https://on...
New
Hello everyone! This thread is to tell you about what authors from The Pragmatic Bookshelf are writing on Medium.
New
Use WebRTC to build web applications that stream media and data in real time directly from one user to another, all in the browser.
...
New
Biggest jackpot ever apparently! :upside_down_face:
I don’t (usually) gamble/play the lottery, but working on a program to predict the...
New
I have always used antique keyboards like Cherry MX 1800 or Cherry MX 8100 and almost always have modified the switches in some way, like...
New
Jan | Rethink the Computer.
Jan turns your computer into an AI machine by running LLMs locally on your computer. It’s a privacy-focus, l...
New
Build modern server-driven web applications using htmx. Whatever programming language you use, you’ll write less (and cleaner) code.
...
New
I’m able to do the “artistic” part of game-development; character designing/modeling, music, environment modeling, etc.
However, I don’t...
New
Hello,
I’m a beginner in Android development and I’m facing an issue with my project setup. In my build.gradle.kts file, I have the foll...
New
Latest in Modern Front-End Development for Rails
Categories:
Sub Categories:
Popular Portals
- /elixir
- /rust
- /wasm
- /ruby
- /erlang
- /phoenix
- /keyboards
- /python
- /js
- /rails
- /security
- /go
- /swift
- /vim
- /clojure
- /java
- /emacs
- /haskell
- /svelte
- /onivim
- /typescript
- /kotlin
- /c-plus-plus
- /crystal
- /tailwind
- /react
- /gleam
- /ocaml
- /flutter
- /elm
- /vscode
- /ash
- /html
- /opensuse
- /deepseek
- /zig
- /centos
- /php
- /scala
- /react-native
- /lisp
- /sublime-text
- /textmate
- /nixos
- /debian
- /agda
- /django
- /deno
- /kubuntu
- /arch-linux
- /nodejs
- /spring
- /ubuntu
- /revery
- /manjaro
- /diversity
- /lua
- /julia
- /markdown
- /v











