A flaky test is a test that is often green, but sometimes red. It may only fail on some PCs...

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Basic validations Read the Rails Guide on ActiveRecord Validations. You should have an overview which kinds of validations are built...

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Besides their default styling properties, HTML elements have a semantic meaning. For example, an h1 tag is usually styled with...

The RSpec matcher tests if two HTML fragments are equivalent. Equivalency means: Whitespace is ignored Types of attribute quotes are...

Rails has the handy controller method send_file which lets us download files easily. We can decide whether the file...

It is generally discouraged to load your JavaScript by a tag in the : The reason is that a tag will pause the DOM parser until the script has loaded and executed. This will delay the browser's first contentful paint. A much better default is to load your scripts with a tag: A deferred script has many...

The attached compiler() function below applies JavaScript behavior to matching HTML elements as they enter the DOM. This works like...

Given you have a strict CSP that only allows elements from your own domain: Content-Security-Policy: script-src 'self' This will block JavaScript handlers inlined as attribute into your HTML elements. Clicking on the following link will only log an error with a strict CSP: click me click me Solution 1: Move the handler into your JavaScript The recommended solution is to move the handler from the HTML to the allowed JavaScript file that we loaded via . In the example above we could invent a new [data-alert] attribute with the alert message: click me Then our JavaScript intercepts clicks on elements with that attribute: document.addEventListener('click', function(event) { let link = event.target.closest('[data-alert]') if (link) { let message = link.dataset.alert alert(message) event.preventDefault() } }) Solution 2: Allow that one handler in your CSP Some browsers allow the CSP directive script-src-attr. This lets you allow the hashes of actual JavaScript code. The SHA256 hash of alert('hello') is vIsp2avtxDy0157AryO+jEJVpLdmka7PI7o7C4q5ABE= (in Base64). We can allow this one event handlers like this: Content-Security-Policy: script-src 'self'; script-src-attr 'unsafe-hashes' 'sha256-vIsp2avtxDy0157AryO+jEJVpLdmka7PI7o7C4q5ABE=' Note the sha256- prefix. This event handler now works when clicked: click me But any other script will still be blocked: click me Dealing with legacy browsers Currently (November 2023) about 75% of browsers support script-src-attr. Here is a forward-looking compromise that many users use with new CSP features: Have a liberal CSP with old directives supported by all browsers Make your CSP stricter with new, more specific directives for browsers that support it The CSP spec supports that approach in that using newer, more specific directives disable older, more general features. In our case this means: For old browsers, allow all inline scripts For new browsers, disallow inline scripts but allow inline handlers with given hashes Here is a CSP directive that works like this: Content-Security-Policy: script-src 'self' 'unsafe-inline'; script-src-elem 'self'; script-src-attr 'unsafe-hashes' 'sha256-vIsp2avtxDy0157AryO+jEJVpLdmka7PI7o7C4q5ABE=' Old browsers will only use script-src. New browsers will use script-src-elem (for tags) and script-src-attr (for inline event handlers), which override the more liberal rules from script-src. Solution 3: Don't use a strict CSP You can have a secure web application without a strict CSP. A Content Security Policy should never be your first line of defense against Cross-Site-Scripting (XSS). Your primary tool should be to escape and sanitize user input. Many template engines make it easy to do the right thing by escaping dynamic content by default. A CSP is a second security net. It's there when you slip up and somehow, somewhere don't sanitize user input. Depending on your project, you may decide to prioritize developer convenience over a strict CSP.

Often people need links which are not linked directly, but should trigger execution of JavaScript. ❌ Bad workarounds

Our gem spreewald supports a few helpers for development. In case you notice errors in your Cucumber tests, you might...

en.wikipedia.org

Formerly 301 (Moved Permanently) and 302 (Found) were used for redirecting. Browsers did implement them in different ways, so since...

When giving a presentation where you do some coding, the font size you usually use is probably a bit too...

When testing JavaScript functionality in Selenium (E2E), you may need to access a class or function inside of a evaluate...

markodenic.com

Table of content for the linked article: 1. The `loading=lazy` attribute 2. Email, call, and SMS links

Matching the "space" character class For matching whitespaces in a regular expression, the most common and best-known shorthand expression...

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Webpack builds can take a long time, so we only want to compile when needed. This card shows what will...

To attach files to your records, you will need a new database column representing the filename of the file...

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In Ruby (almost) everything is an Object. While this enables a lot of powerful features, this concept might be confusing...

The ActionDispatch module of Rails gives you the helper method flash to access the flash messages in a response.

CarrierWave comes with a set of default configuration options which make sense in most cases. However, you should review these...

getbootstrap.com

Recently I made an upgrade from Bootstrap 3 to Bootstrap 4 in a bigger project. Here are some tips how...

Consider the following models and form models: class Parent < ApplicationRecord has_many :children, class_name: 'Child', foreign_key: 'parent_id...

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Rails 6 includes a WYSIWYG editor, Action Text. It works out of the box quite well, but chances are that...

Rails supports alert and notice as default flash types. This allows you to use these keys as options in e.g...