Mature and modular cross-browser JS library/framework. All feature testing, all the time. Never heard of the UA string. Dynamic API supports (practical) progressive enhancement. Virtually bullet-proof in new (and old) environments (e.g. new browser versions, new devices, etc.) Rarely updated over the years (and never by necessity to "catch up" with new browsers). Best to propose changes *before* starting work (will likely save time). Changes rationalized by "show me where it fails" will be dismissed out of hand, as will browser sniffs, conditional compilation, mystical incantations, etc. Best of luck. You have our gratitude.