Not that I know of. Gnome Shell makes heavy use of JavaScript, but in a way unrelated to GTK+ itself. JavaScript bindings are of course also nothing new in the Qt world; KDE has had KJSEmbed for many years to write KDE/Qt apps in JavaScript, and Qt itself offers QtScript to generate ECMAScript bindings to Qt APIs for years as well.
Qt 5 goes quite bit beyond simply allowing you to access traditional C++-style APIs from JavaScript, however, it essentially implements an all-new UI toolkit based around a declarative language dubbed QML that is actually JavaScript and lets you jot down UIs and their behaviors in a sort of JSON-plus-logic fashion.
Qt 5 goes quite bit beyond simply allowing you to access traditional C++-style APIs from JavaScript, however, it essentially implements an all-new UI toolkit based around a declarative language dubbed QML that is actually JavaScript and lets you jot down UIs and their behaviors in a sort of JSON-plus-logic fashion.