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// Copyright (C) 2017 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
/*!
\page qtqml-javascript-topic.html
\title Integrating QML and JavaScript
\brief Description of how to use JavaScript in QML applications
The QML language uses a JSON-like syntax and allows various expressions and
methods to be defined as JavaScript functions. It also allows users to import
JavaScript files and use the functionality those imports provide.
This allows developers and designers to leverage the knowledge they have of
JavaScript to quickly develop both user-interfaces and application logic.
\section1 JavaScript Expressions
QML has a deep JavaScript integration, and allows \l{Signal Attributes}
{signal handlers} and \l{Method Attributes}{methods} to be defined in JavaScript.
Another core feature of QML is the ability to specify and enforce relationships
between object properties using \l{Property Binding}{property bindings}, which
are also defined using JavaScript.
See the documentation page titled
\l{qtqml-javascript-expressions.html}{JavaScript Expressions in QML Documents}
for more information about using JavaScript expressions in QML.
\section1 Dynamic QML Object Creation from JavaScript
QML supports the dynamic creation of objects from within JavaScript. This is
useful to delay instantiation of objects until necessary, thereby improving
application startup time. It also allows visual objects to be dynamically
created and added to the scene in reaction to user input or other events. This
functionality can be used in two main ways.
Object can be created dynamically from JavaScript in an imperative way using
\l{qtqml-javascript-dynamicobjectcreation.html}{dynamic creation of objects}.
This can be useful, for example, when QML is used as an application scripting
language.
\note When creating user interfaces, the preferred way of creating objects
dynamically is to use declarative constructs as these integrate best with the
QML engine and tooling. Various types exist to enable this functionality such
as the \l{Loader}, \l{Instantiator}, \l{Repeater} types.
\section1 JavaScript Resources
Application logic defined in JavaScript functions may be separated into
separate JavaScript files known as JavaScript resources. There are several
different kinds of JavaScript resources, with different semantics.
See the documentation page titled \l{qtqml-javascript-resources.html}
{Defining JavaScript Resources In QML} for more information about defining JavaScript
resources for QML.
\section1 JavaScript Imports
A QML document may import JavaScript resources, and JavaScript resources may
import other JavaScript resources as well as QML modules. This allows an
application developer to provide application logic in modular, self-contained
files.
See the documentation page titled
\l{qtqml-javascript-imports.html}{Importing JavaScript Resources}
for more information on how to import JavaScript resources and how to use the
functionality they provide.
\section1 JavaScript Host Environment
The QML engine provides a JavaScript environment that has some differences to
the JavaScript environment provided by a web browser. Certain limitations
apply to code running in the environment, and the QML engine provides various
objects in the root context which may be unfamiliar to JavaScript developers.
These limitations and extensions are documented in the description of the
\l{qtqml-javascript-hostenvironment.html}{JavaScript Host Environment} provided
by the QML engine.
There is also an in depth description of the
\l{qtqml-javascript-memory.html}{memory management} employed by the JavaScript
engine.
\section1 Configuring the JavaScript engine
For specific use cases you may want to override some of the parameters the
JavaScript engine uses for handling memory and compiling JavaScript. See
\l{qtqml-javascript-finetuning.html}{Configuring the JavaScript engine} for
more information on these parameters.
*/
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