When deploying with capistrano it's possible you get this "error" message:

*** [err :: example.com] There are no Phusion Passenger-served applications running whose paths begin with '/var/www/example.com'.
*** [err :: example.com] 

This is just because there were no running passenger process for this application on the server which could be restarted. It's not a real error. The application process will start if the first request for this app hits the appserver.

The output appears as err because it's printed to stderr.

Dep…

If you get requests with values for formats like this:

{:locale=>[:de], :formats=>["../../../../../../../../../../etc/services{{"], :variants=>[], :handlers=>[:erb, :builder, :raw, :ruby, :coffee, :haml]}

or fails like this:

Invalid query parameters: invalid %-encoding (../../../../../../../../../etc/passwd%%0000.html)

Someone tries to exploit CVE-2019-5418.
If you use the latest Rails (or latest Rails LTS) you're…

The CSS property z-index is not as global as you might believe. Actually, it is scoped to a so-called "stacking context". z-indexes only have meaning within their stacking context, while stacking contexts are treated as a single unit in their parent stacking context. This means indices like 99999 should never actually be needed.

Creating a new stacking context

In order to create a stacking context with the least possible side effects, use these properties on an element:

```
position: relative // or absolute
z-index: 0 // o…

Is your application doing something expensive every few seconds? Maybe an animated slider that rotates images? Maybe you are updating data over the network every five minutes?

It's a good idea to pause this if the your document tab is not even visible to the user. This saves your user's battery and data plan.

You can ask document.visibilityState whether this tab is visible:

```
function pulse() {
if (!document.visibilityState || document.visibilityState =…

Webpacker can automatically create an icon font from SVG files, which is really handy. When you're using the asset pipeline, you can still have an icon font from SVG files, but it requires some manual work.

Creating the icon font

• Install the NPM package icon-font-generator. If you're not using nvm, run sudo npm install -g icon-font-generator
• Put all SVG icons for the font into their own directory.
  • The icon name will be taken from the SVG file name
• Download the attached script and update the Configure…

Unpoly 0.60.0 removed the jQuery dependency to improve performance (see Hennings talk about Javascript without jQuery). I upgraded one of our applications which used a lot of JavaScript with Unpoly compilers and jQuery and want to mention some aspects I had trouble with:

Use up.$compiler as a first step

up.compiler now yields a native DOM element instead of jQuery element. In order to get the old behavior, use up.$compiler. This is u…

jQuery has a function $.fn.trigger(). You can use it to dispatch an event on a jQuery object:

let $element = $('.foo')
$element.trigger('change')

A caveat is that such an event will be received by jQuery event listeners, but not by native event listeners:

let $element = $('.foo')

$element.on('change', event => console.log('I will be called'))
$element[0].addEventListener('change', event => console.log('I WON'T be called'))

$element.trigger('change')

This is currently a WONTFIX for jQuery (see c…

It is quite easy to migrate from CoffeeScript to ES6. You can use decaffeinate to convert your CoffeeScript source to modern JavaScript.

Installation

• Install the NPM module globally yarn global add decaffeinate
• Add the following line to your ~/.bashrc to export the Yarn binaries in your Bash

export PATH="$PATH:$(yarn global bin)"

• Run decaffeinate some.coffee to get the converted modern JavaScript file.

Notes

• decaffeinate will add some [suggestions](https://gith…

So you are comparing two Time objects in an RSpec example, and they are not equal, although they look equal:

expected: Tue May 01 21:59:59 UTC 2007,
     got: Tue May 01 21:59:59 UTC 2007 (using ==)

The reason for this is that Time actually tracks fractions of a second, although #to_s doesn't say so and even though you probably only care about seconds. This means that two consecutive calls of Time.now probably return two inequal values.

Consider freezing time in your tests so it is not dependent on the speed of the executi…

TLDR: Ruby class variables (@@foo) are dangerous in many ways. You should avoid them at all cost. See bottom of this card for alternatives.

Class variables are shared between a class hierarchy

When you declare a class variable, it is shared between this and all descending (inheriting) classes. This is rarely what you want.

Class variables are bound at compile-time

Like unqualified constants, class variables are bound to your current scope *whe…

In a nutshell: return statements inside blocks cause a method's return value to change. This is by design (and probably not even new to you, see below) – but can be a problem, for example for the capture method of Rails.

Consider these methods:

def stuff
  puts 'yielding...'
  yield
  puts 'yielded.'
  true
end

We can call our stuff method with a block to yield. It works like t…

Over the years we have tried several solution to have vector icons in our applications. There are many ways to achieve this, from SVGs inlined into the HTML, SVGs inlined in CSS, JavaScript-based solutions, to icon fonts.

Out of all these options, the tried and true icon font seems to have the most advantages, since

• icon fonts are supported everywhere
• they perform well and require no JavaScript at all
• their icons align nicely with text
• their icons automatically inherit color and size of the surrounding text

The big issue used to b…

To keep JavaScript sources small, it can sometimes make sense to split your webpack bundles. For example, if your website uses some large JavaScript library – say TinyMCE – which is only required on some select pages, it makes sense to only load that library when necessary.

In modern webpack this is easily doable by using the asynchronous import function.

Say we have an unpoly compiler that sets up TinyMCE like this (code is somewhat simplified):

```
// TinyMCE as part of the main bundle!

import tinymce from 'tinymce/tinymce'

// UI
im…

We already have some approaches on how to test file downloads withe selenium. Nonetheless here is another approach, which inspects the Chrome download folder. This way you do not need a separate logic on whether a file is served from a controller or a public path. The DownloadHelpers might also be re-used for reading e.g. a PDF file and checking its content.

Note: The step below will override a [spreewald step](https://gith…

We're always striving towards keeping our website's JavaScript as small as possible.

If you're using webpack(er), you can use the webpack-bundle-analyzer plugin to get a good overview, which of your JavaScript modules take up how much space, and where you can optimize.

To use it, add it via npm or yarn

yarn add webpack-bundle-analyzer

Then add this to your environment.js:

```
// Uncomment this code to show statistics of bundle sizes. Generated file will automatically o…