JavascriptEngine Class Reference

This class is a wrapper around QuickJS, an ES2023 compliant, embeddable javascript engine. More...

Public Member Functions
	JavascriptEngine ()
	Creates an instance of the engine.
	~JavascriptEngine ()
	Destructor.
Result	execute (const String &javascriptCode)
	Attempts to parse and run a block of javascript code.
var	evaluate (const String &javascriptCode, Result *errorMessage=nullptr)
	Attempts to parse and run a javascript expression, and returns the result.
var	callFunction (const Identifier &function, const var::NativeFunctionArgs &args, Result *errorMessage=nullptr)
	Calls a function in the root namespace, and returns the result.
void	registerNativeObject (const Identifier &objectName, DynamicObject *object)
	Adds a native object to the root namespace.
void	stop () noexcept
	When called from another thread, causes the interpreter to time-out as soon as possible.
JSObject	getRootObject () const
	Returns the object from which all Javascript objects are reachable in the engine's context.
NamedValueSet	getRootObjectProperties () const
	Provides access to the set of properties of the root namespace object.

Public Attributes
RelativeTime	maximumExecutionTime
	This value indicates how long a call to one of the evaluate methods is permitted to run before timing-out and failing.

Detailed Description

This class is a wrapper around QuickJS, an ES2023 compliant, embeddable javascript engine.

It may not be as fast as the fancy JIT-compiled engines that you get in browsers, but this is an extremely compact, low-overhead javascript interpreter, which is integrated with the juce var and DynamicObject classes. It allows you to easily let the JS work with native objects defined as DynamicObject subclasses.

To use, simply create an instance of this class and call execute() to run your code. Variables that the script sets can be retrieved with evaluate(), and if you need to provide native objects for the script to use, you can add them with registerNativeObject().

Constructor & Destructor Documentation

JavascriptEngine()

JavascriptEngine::JavascriptEngine

(

)

Creates an instance of the engine.

Referenced by getRootObjectProperties().

~JavascriptEngine()

JavascriptEngine::~JavascriptEngine

(

)

Destructor.

Member Function Documentation

execute()

Result JavascriptEngine::execute

(

const String &

javascriptCode

)

Attempts to parse and run a block of javascript code.

If there's a parse or execution error, the error description is returned in the result. You can specify a maximum time for which the program is allowed to run, and it'll return with an error message if this time is exceeded.

evaluate()

var JavascriptEngine::evaluate	(	const String &	javascriptCode,
		Result *	errorMessage = nullptr )

Attempts to parse and run a javascript expression, and returns the result.

If there's a syntax error, or the expression can't be evaluated, the return value will be var::undefined(). The errorMessage parameter gives you a way to find out any parsing errors. If the expression is successfully evaluated but yields no result the return value will be a void var. You can specify a maximum time for which the program is allowed to run, and it'll return with an error message if this time is exceeded.

callFunction()

var JavascriptEngine::callFunction	(	const Identifier &	function,
		const var::NativeFunctionArgs &	args,
		Result *	errorMessage = nullptr )

Calls a function in the root namespace, and returns the result.

The function arguments are passed in the same format as used by native methods in the var class.

registerNativeObject()

void JavascriptEngine::registerNativeObject	(	const Identifier &	objectName,
		DynamicObject *	object )

Adds a native object to the root namespace.

The object passed-in is reference-counted, and will be retained by the engine until the engine is deleted. The name must be a simple JS identifier, without any dots.

stop()

void JavascriptEngine::stop ( )

noexcept

When called from another thread, causes the interpreter to time-out as soon as possible.

getRootObject()

JSObject JavascriptEngine::getRootObject

(

)

const

Returns the object from which all Javascript objects are reachable in the engine's context.

References getRootObject().

Referenced by getRootObject().

getRootObjectProperties()

NamedValueSet JavascriptEngine::getRootObjectProperties

(

)

const

Provides access to the set of properties of the root namespace object.

References getRootObjectProperties(), JavascriptEngine(), JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR, and JUCE_DECLARE_NON_MOVEABLE.

Referenced by getRootObjectProperties().

Member Data Documentation

maximumExecutionTime

RelativeTime JavascriptEngine::maximumExecutionTime

This value indicates how long a call to one of the evaluate methods is permitted to run before timing-out and failing.

The default value is a number of seconds, but you can change this to whatever value suits your application.