Here is an ES5 object literal with two string properties and a function property:

let user = { 
  firstName: 'Max',
  lastName: 'Muster',
  fullName: function() { return this.firstName + ' ' + this.lastName }
}

user.fullName() // => 'Max Muster'

In ES6 we can define a function property using the following shorthand syntax:

let user = { 
  firstName: 'Max',
  lastName: 'Muster',
  fullName() { return this.firstName + ' ' + this.lastName }
}

user.fullName() // => 'Max Muster'

We can also define a gette...

Speaker today is Henning Koch, Head of Development at makandra.

This talk will be in German with English slides.

Introduction

As web developers we work with JavaScript every day, even when our backend code uses another language. While we've become quite adept with JavaScript at a basic level, I think many of us lack a deep understanding of the JavaScript object model and its capabilities.

Some of the questions we will answer in this talk:

• How does the new keyword construct an object?
• What is the differen...

Let's say you want to merge the properties of two JavaScript objects:

let a = { foo: 1, bar: 2 }
let b = { bar: 3, baz: 4 }

let merged = merge(a, b) // => { foo: 1, bar: 3, baz: 4 }

Depending on your build, there are several ways to implement merge().

When you have ES6

When you have an ES6 transpiler or don't support IE11, you may use the spread operator (...) to expand both objects into a new object literal:

let merg...

Test Driven Development is the paradigm to "first write a test, then implement the code". This guide shows how to apply it in practice, with Cucumber and RSpec as integration and unit test frameworks.

Hierarchical approach

I like to view TDD as a process with three levels:

• Cucumber level (integration test)
• Code level
• RSpec level (unit test)

During development you are frequently changing levels. It may look something like this:

Integration _                    _
Code         \__      ___     __/
Spec            \____/   \__...

Typhoeus has a different way of representing array params in a get request than RestClient.

Typhoeus: http://example.com/?foo[0]=1&foo[1]=2&foo[2]=3
RestClient: http://example.com/?foo[]=1&foo[]=2&foo[]=3

Webmock normalizes this url when matching to your stubs, so it is always http://example.com/?foo[]=1&foo[]=2&foo[]=3. This might lead to green tests, but in fact crashes in real world. Rack::Utils.build_nested_query might help to build a get re...

RubyMine has a HTTP Client that can be useful to test web APIs.
Just create a .http scratch file an write your request in it.
The request can then be executed with the "Run all requests in File" button above the file.

Some alternatives:
Postman
Curl

The format for request is like this:

Method Request-URI HTTP-Version
Header-field: Header-val...

In a web application you sometimes have tasks that can not be processed during a request but need to go to the background.
There are several gems that help to you do that, like Sidekiq or Resque.

With newer Rails you can also use ActiveJob as interface for a background processing library. See here for a list of supported queueing adapters.
For ...

You cannot use Array#join on an array of strings where some strings are html_safe and others are not. The result will be an unsafe string and will thus be escaped when rendered in a view:

unsafe_string = '<span>foo</span>'
safe_string = '<span>bar</span>'.html_safe
[unsafe_string, safe_string].join(' ') # will incorrectly render as '&lt;span&gt;foo&lt;/span&gt;&lt;span&t;bar&lt;/span&gt;'

Bad

The solution is not to call html_safe on the joined array and if you thought it would be, you [don't understand how XSS protecti...

In case you want to use pry with an older version of Ruby, you can try the following configurations.

Ruby 1.8.7

Your pry version must not be greater than 0.9.10.

gem 'pry', '=0.9.10'
gem 'ruby-debug'
gem "ruby-debug-pry", :require => "ruby-debug/pry"
gem 'pry-nav'
gem 'ruby18_source_location'

Ruby 1.9.3

Your pry version must not be greater than 0.9.9.

gem 'debugger', '=1.1.4'
gem 'pry-debugger', '=0.2.0'
gem 'pry', '=0.9.9'

Known errors

No source for ruby-1.9.3-p551 p...

When storing floating-point numbers such as prices or totals in an SQL database, always use a DECIMAL column. Never use FLOAT or kittens will die.

DECIMAL columns are parametrized with a precision and a scale. These parameters describe which numbers can be stored in that column. E.g. a decimal with a precision of 5 and a scale of 2 can store numbers from -999.99 to 999.99, but not 1000 or 1.234.

This card explains what various databases do when you try to store a number in a DECIMAL field, and that number exceeds that colum...

simple_format ignores Rails' XSS protection. Even when called with an unsafe string, HTML characters will not be escaped or stripped!

Instead simple_format has a whitelist of tags it allows. These are:

ActionView::Base.sanitized_allowed_tags
=> #<Set: {"small", "dfn", "sup", "sub", "pre", "blockquote", "ins", "ul", "var", "samp", "del", "h6", "h5", "h4", "h3", "h2", "h1", "span", "br", "hr", "em", "address", "img", "kbd", "tt", "a", "acronym", "ab...

Webpacker uses Babel and Webpack to transpile modern JavaScript down to EcmaScript 5. Depending on what browser a project needs to support, the final Webpack output needs to be different. E.g. when we need to support IE11 we can rely on fewer JavaScript features. Hence our output will be more verbose than when we only need support modern browsers.

Rails 5.1+ projects often use Webpacker to preconfigure the Webpack pipeline for us. The default configuration works something like this:

1. Webpack checks w...

We use CarrierWave in many of our projects to store and serve files of various formats - mostly images. A common use case of CarrierWave's DSL is to "process" the original file in order to create multiple "versions", for example different resolutions of the same image.

Now we could go one step further: What if we want to create versions that have a different file extension than the original file? For example, let's assume we'd like to create a ve...

With Ruby's build-in library English you can reference global variables with an english name. This makes you code easier to read and is also suggested by Rubocop's Style/GlobalVars cop.

Example before:

if 'foo' =~ /foo/
  puts $~[1] # => foo
end

Example after:

if 'foo' =~ /foo/
  puts $LAST_MATCH_INFO[1] # => foo
end

Require pitfall in Rails

The English library is not loaded by default in Rails. S...