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Building web applications: Beyond the happy path

When building a web application, one is tempted to claim it "done" too early. Make sure you check this list.

Different screen sizes and browsers

Desktops, tablets and mobile devices have all different screen resolutions. Does your design work on each of them?

  • Choose which browsers to support. Make sure the page looks OK, is usable and working in these browsers.
  • Use @media queries to build a responsive design
    • If you do not suppo…
Linked content

How to: expand an element's cover area beyond its container

Occasionally, your designer will hand you designs where elements break the layout's horizontal container width, like navigation buttons of a slider that should be at the left/right of the browser window, or simply by applying a background color that reaches until the left and right of the browser window.

In the past, we've done some horrible things to achieve that. Like margin: 0 -10000px plus overflow-x: hidden.
There is a much saner approach.

Consider the following markup:

```html

<div class="sec...

How to access before/after pseudo element styles with JavaScript

Accessing pseudo elements via JavaScript or jQuery is often painful/impossible. However, accessing their styles is fairly simple.

Using getComputedStyle

First, find the element in question.

let element = document.querySelector('.my-element') // or $('.my-element').get(0) when using jQuery

Next, use JavaScript's getComputedStyle. It takes an optional 2nd argument to filter for pseudo elements.

```javascript
let style = window.getComputedStyle(element, '::before')
let color = style.getPropertyValue('background-color…

Repeats

Don't forget: Automatically remove join records on has_many :through associations

Bad

# Given the following models

class Image < ActiveRecord::Base
  has_many :album_image
  has_many :albums, through: :album_images
end

class Album < ActiveRecord::Base
  has_many :album_image
  has_many :images, through: :album_images
end

# Join model
class AlbumImage < ActiveRecord::Base
  belongs_to :album
  belongs_to :image
end

Destroying a record in this setup will only remove the record itself, and leave orphaned join records behind.

```
image = Image.last
image.destroy # removes only the image record,

Fixing "identify: not authorized"

Ubuntu has decided to disable PDF processing because ImageMagick and the underlying Ghostscript had several security issues.

When your Ghostscript is up to date (and receiving updates regularly), you can safely reactivate PDF processing on your computer like this:

  1. Open /etc/ImageMagick-6/policy.xml
    • For older versions of Ubuntu (or possibly ImageMagick, the Path is /etc/ImageMagick/policy.xml
  2. Remove/Comment lines after <!-- disable ghostscript format types -->

If you need it enabled for an…

Linked content

Drawing diagrams with draw.io

draw.io is a web application that lets you draw flow charts and other diagrams. It works much nicer than office suite tools like LibreOffice Draw.

Its UI is easy to use: Simply drag and drop shapes or arrows from the left-hand side onto your sheet. Drag start/end of arrows to shapes to automatically connect them. You can add text to shapes by selecting them and typing. To add colors, select a shape and use the right-hand panel.

While you can, you don't need to store your charts online. "Offline" storage can be files…

An incomplete guide to migrate a Rails application from paperclip to carrierwave

In this example we assume that not only the storage gem changes but also the file structure on disc.

A general approach

Part A: Create a commit which includes a script that allows you to copy the existing file to the new file structure.

Part B: Create a commit which removes all paperclip logic and replace it with the same code you used in the first commit

Part A

Here are some implementation details you might want to reuse:

  • Use the existing models to read the files from
  • Use your own carrierwave models to write t…

Introduction to Google Tag Manager (for web developers who know Google Analytics)

As a web developer, you know Google Analytics (GA). Probably you've dropped the GA snippet into more than one website, maybe you've even used its Javascript API to implement tracking at the event level.

Google Tag Manager (GTM) is a related tool, but on a higher level and thus with much more power. GTM is not a replacement for GA. Rather, it can make GA configurable without changing anything in the application's code base (and much more beyond, see below).

Only prefer GTM if the customer requests it, or if he is updating his tracking r…

Repeats

Do not use transparent PNGs for iOS favicons

Safari on iOS accepts an apple-touch-icon favicon that is used for stuff like desktop bookmarks. Always define a solid background color for them.

If you use PNGs with a transparent background, Safari will use just set a black background on your pretty icon. This is almost never what you want.
You can fix that by applying a white background via ImageMagick like this:

convert a...
Repeats

Optimizing images for web

For webpages to load fast it's recommended to optimize images. Ideally an image's file size should be as small as possible while still being of decent quality. This card demonstrates two command line tools for image optimization

Use identify to fetch information about pictures. convert can change size/quality and strip meta information. Both commands are supplied by ImageMagick.

```text
$ identify in.jpg
in.jpg JPEG 294x440 294x440+0+0 8-bit sRGB 92.8KB 0.000u 0:00.000
$ convert in.jpg -resize x220 -strip -quality 85 out.jpg
$ identify…

Repeats

Ruby constant lookup: The good, the bad and the ugly

In Ruby, classes and modules are called constants. This card explains how Ruby resolves the meaning of a constant.

The good

E. g. in the following example, Array could mean either Foo::Array or simply Array:

class Foo
  def list
    Array.new
  end
end

What Ruby does here is to see if the name Array makes sense inside of Foo::, and if that fails, resolves it to ::Array (without a namespace).

The bad

You might be surprised that these are all valid ways to reference Ruby's String class:

Linked contentRepeats

Designing HTML email

The 90s are calling: they want their tables back. Unfortunately, you'll need them all for laying out your HTML emails. (It is really that bad.)

Email client HTML rendering is way more scattered than browser HTML. While you might have a pretty good understanding of what features and patterns you can use to support all major browsers, I doubt anyone masters this craft for HTML email clients.

The only way to ensure your email looks good (acceptable, at least) in all mail clients, is to check it. Litmus is your go-to solu…

Linked content

Using the Ruby block shortcut with arguments

Ruby has this handy block shortcut map(&:to_i) for map { |x| x.to_i }. However, it is limited to argument-less method invocations.

To call a method with an argument, you usually need to use the full block form. A common case is retrieving values from a list of hashes (imagine using a JSON API):

users = [ { name: 'Dominik', color: 'blue' }, { name: 'Stefan', color: 'red'} ]
names = users.collect do |user|
  user['name']
end

But with a little extension, you can do better.

Block shortcut with arguments

By defining `Symbol#c…

Linked content

CSS: Using interaction media detection to disable hover styles for devices that have no hover

Since late 2015, all major browsers (still excluding Firefox) support pointing device media queries. These can be used to distinguish e.g. coarse from fine pointers (e.g. finger vs mouse), or a device with hover support from one without (e.g. desktop with mouse vs tablet).

Motivation

When hover styles modify the DOM, most mobile devices activate the hover styles on first tap. A second tap is required to trigger a click. While this can be handy, at times it makes the UX worse.

Another issue with hover styles is that they tend to st…

Repeats

How to make your application assets cachable in Rails

Note: Modern Rails has two build pipelines, the asset pipeline (or "Sprockets") and Webpacker. The principles below apply for both, but the examples shown are for Sprockets.


Every page in your application uses many assets, such as images, javascripts and stylesheets. Without your intervention, the browser will request these assets again and again on every request. There is no magic in Rails that gives you automatic caching for assets. In fact, if you haven't been paying attention to this, your application is probabl…

Linked contentRepeats

Printing background color of elements

Browsers' printing methods usually don't print background colors. In most cases this is the desired behavior, because you don't want to spent tons of ink printing the background of a web page. But in some cases you want to print the background color of elements, e.g. bars of a chart. For those elements you need to set the following css styles:

Chrome and Safari:

-webkit-print-color-adjust: exact;

Firefox:

color-adjust: exact;
Repeats

Stretching an HTML page to full height

This card existed before, but was outdated due to browser implementation changes. The information below is validated for the current list of browsers we support.


By default your html and body elements are only as high as the actual page content. If you only have two lines of text in your page, your html and body elements will only be around 40 pixels high, regardless of the size of your browser window.

You might be surprised by this, since setting a background on either html and body does cover the enti…

Linked content

CSS: Using the current text color for other color properties

There is a kinda secret, yet well supported CSS feature called currentColor. It's like a special CSS variable that has been supported in almost all browsers for almost all time (see linked Caniuse).

Usage

The currentColor value can be used in CSS to indicate the current value of color should be used. A common use case is setting a border color:

a.ghost
  color: white
  border: 1px solid currentColor
  &:hover
    color: red // Border color will change as well 

Note that in many cases, you can simply omit the color to ac…

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