QJS

QJS is a JavaScript engine and runtime designed for embedding in applications, with particular emphasis on the Qt ecosystem. It provides a bridge between JavaScript and C++, enabling scriptability of Qt applications and QML components. The engine is commonly referred to in the Qt context as the Qt JavaScript engine, and it is distributed as part of the Qt framework.

Origin and development: QJS evolved as part of Qt’s effort to replace older scripting solutions with a modern, lightweight JavaScript backend that integrates well with Qt types and the Qt event loop. It is implemented to work alongside other Qt scripting APIs, such as QJSValue and related classes, and has been maintained across multiple Qt releases to support both Qt 5 and Qt 6 environments.

Architecture and features: QJS provides an embeddable JavaScript runtime that allows applications to evaluate scripts, call JavaScript functions, and exchange data with C++ via QVariant-friendly conversions. It integrates with Qt’s event loop to support asynchronous tasks and offers bindings to Qt types, enabling properties, signals, and slots to be used from JavaScript. The engine is designed with safety considerations for hosting user scripts and includes hooks for debugging within Qt tooling.

Usage and scope: It is used to add runtime scripting to Qt applications, implement dynamic configuration, or extend QML with custom JavaScript modules. While not a general-purpose replacement for standalone JavaScript engines, QJS provides a stable, Qt-focused path for embedding JavaScript in Qt projects.

See also: QJSEngine, QJSValue, QML, Qt Script.