Replacing DOM fragments with innerHTML wipes state such as form values, scroll position, and custom-element data. morphdom and idiomorph preserve existing nodes by applying minimal changes.

Custom Angular test bootstraps centralize global providers, matchers, and test-wide setup while preserving CLI strict error checking.

Checklist for CarrierWave edge cases beyond the default Rails setup: secure URLs, image resizing, metadata handling, file validation, and efficient processing.

Bare rescue swallows StandardError and hides typos and other unexpected failures. Rescue only the specific exception you expect so monitoring still catches real bugs.

DOM-based Jasmine specs can leak leftover elements into later tests; using a dedicated fixture container cleared after each run keeps test state isolated.

Modern browsers can read selected folders and files with the File System Access API, reducing the need for ZIP upload workarounds when recursive directory handling is enough.

A unique index on a has_one foreign key lets the database enforce 1:1 relationships and fail fast when application logic creates duplicate rows.

inverse_of lets Rails treat both sides of an association as the same in-memory object, reducing duplicate loads and fixing bi-directional association behavior.

Updating one gem with bundle update can pull in dependency upgrades and break existing code. Bundler --conservative limits changes to the targeted gem and avoids unnecessary transitive updates.

Trait parameters require define_singleton_method for class-level behavior; def self.foo works only without parameters, with normal class method visibility caveats.

Local Sentry event logging helps debug error capture and background jobs without sending data to Sentry or affecting production metrics.

Trigram indexes provide a lightweight alternative when full-text search becomes too rigid or slow. A virtual column can combine multiple text fields and support indexed LIKE queries.

Building Bootstrap forms with simple_form reduces repetitive markup and keeps form layouts consistent.

return, break, and next behave differently in Ruby blocks: one exits the method, one exits the yielding method, and one skips only the current iteration.

ActiveRecord threads can open one database connection per thread, quickly exhausting server limits. Rails reuses and releases connections automatically, but manual cleanup is sometimes needed.

Rails data can be passed to Unpoly compilers through data-* for simple strings and up-data for objects, arrays, and nested values.

Common Unpoly compiler selector strategies for reusable components, one-off view behavior, configurable attributes, and universal element enhancements.

Keeping project estimates aligned with the remaining budget prevents overruns when requirements change and project management overhead shifts.

Passing last_modified without an object skips ETag generation, so second-level timestamps can make distinct responses look identical and break cache-related tests.

Events from controls inside a disabled fieldset stop bubbling in Firefox, unlike Chrome and IE/Edge, which can break document-level listeners and delegated handlers.

Large-table COUNT(*) queries can be slow when only a threshold like 100+ matters; a LIMITed subquery stops early and avoids scanning every row.

RSpec truncates long inspected values to 200 characters, which can hide the real cause of failing specs. Raising max_formatted_output_length reveals more of the error message.

Ruby 1.9+ \w and \d stay ASCII-only; Unicode-aware POSIX character classes match letters, digits, and other script-specific characters.

Pause expensive periodic work when a tab is hidden to save battery and mobile data; document.hidden and visibilitychange let background pages go passive.