# Advanced Techniques ## Performance of QML QML and Javascript are interpreted languages. This means that they do not have to be processed by a compiler before being executed. Instead, they are being run inside an execution engine. However, as interpretation is a costly operation, various techniques are used to improve performance. The QML engine uses just-in-time (JIT) compilation to improve performance. It also caches the intermediate output to avoid having to recompile. This works seamlessly for you as a developer. The only trace of this is that files ending with `qmlc` and `jsc` can be found next to the source files. If you want to avoid the initial start-up penalty induced by the initial parsing you can also pre-compile your QML and Javascript. This requires you to put your code into a Qt resource file, and is described in detail in the [Compiling QML Ahead of Time](https://doc.qt.io/qt-6/qtquick-deployment.html#ahead-of-time-compilation) chapter in the Qt documentation. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.novaflowos.com/start/qt6-qml-book/readme/ch04-qmlstart/advanced.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.