Ruby

Rails 4.2.6 and 4.1.15 have been released, Suppress save events in Rails 5 и Rails 5 switches from strong etags to weak etags
PostgreSQL and Rails, sitting in a tree и GraphQL Ruby: Clean Up your Query Type
Adventures in Production Rails Debugging и Surrogate WebSockets Alongside Rails
DuckRails — is a development tool, which allow developers to quickly mock API endpoints, Unicode::Confusable — compares two strings if they are visually confusable и URN Build Status — Ruby library to validate and normalize URNs according to RFC 2141

JavaScript

React v15.0 Release Candidate и The end of the magic of Meteor
Service Workers: save your user’s data using the save-data header, и 5 Tips For Writing More Maintainable JavaScript Code
Become a 10x programmer. Sharpen your Axe, Styling Broken Images и Enduring CSS (book)
Artillery is a tool for load-testing HTTP and WebSocket-based applications, CryptoIdentity.js — a library for simple crypto identity in the browser и Freezeframe.js is a script that pauses animated .gifs