Webpacker 4 and Babel 7 change config files, package names, asset paths, and polyfill imports when upgrading a Rails app from Webpack 3.

Rails merges query string, request body, and routing data in params; request.query_parameters and request.path_parameters separate URL values from route data.

A float-clearing Sass mixin can avoid extra markup while preserving margin collapse and visible overflow. display: block is a safer clearfix choice than display: table or overflow: hidden.

Flash-free copy-to-clipboard handling with clipboard.js, including success and error callbacks, text selection feedback, and support for text fields or data attributes.

Moving away from jQuery improves performance, reduces bundle size, and aligns with the modern web platform. Native DOM APIs and polyfills now cover most common needs.

Bundler 2 needs Ruby 2.3.0+ and RubyGems 2.5.0+; older Ruby versions require installing the last Bundler 1 release with gem install bundler -v '~>1'.

AngularJS elements can flash visible before bindings apply. ng-cloak hides content until Angular loads; preadding ng-hide also prevents flicker but relies on internals.

Built-in CarrierWave image resizing helpers preserve aspect ratio, crop, or pad images to target dimensions, with MiniMagick and RMagick offering the same methods.

PostgreSQL fulltext search misses partial matches in dates, serial numbers, and other token fragments. Trigram indexes speed up wildcard LIKE searches on large tables.

Removing every table while keeping the PostgreSQL database can be done by dropping the schema or iterating through tables with DROP TABLE statements.

bundle install fails with Gem::GemNotFoundException when Bundler 2 runs on RubyGems 2; updating RubyGems to 3.0+ restores the bundle executable.

Uncountable Rails resources break normal route helpers and form handling. resource can still expose the index action through a special _index_path helper.

Basic Auth sends credentials as a Base64-encoded username:password string in the Authorization header; Ruby can generate it with Base64.strict_encode64.

Ruby can read and write CSV files with the standard CSV library, and smarter_csv makes imports more convenient when converting rows into hashes.

System-specific font fallbacks can make text look different across machines; Chrome DevTools can reveal the actual rendered font in the Computed panel.

Single-threaded Puma in development avoids overlapping requests and noisy console output when debugging. Setting -t 0:1 makes other requests wait.

Cucumber can list step definitions separately, helping detect dead or duplicate steps before cleanup. --dry-run and --format stepdefs reveal candidates, but nested step calls can look unused.

Association values in Machinist blueprints need blocks so Project.make runs per blueprint instance, not once at parse time when RSpec loads.

Upgrading Rails across major versions needs staged updates, compatible Ruby and gem versions, and repeated checks in console, server, tests, and config defaults.

Ace editor adds syntax highlighting and auto-indenting for in-browser code editing, with a working brace setup for Ruby on Rails Webpacker and Webpack 2.

l= shows the current file and line in byebug or ruby-debug; where and backtrace print the debugger call stack.