libjsapi

A SpiderMonkey 50 (Mozilla) JSAPI wrapper for C++ 11.

The JSAPI interface to the SpiderMonkey JavaScript VM can be difficult to integrate into applications without an intermediate abstraction layer managing object creation, object lifetimes and type mapping. This library is an attempt to hide the complexity of dealing with SpiderMonkey from modern C++ 11 applications.

With libjsapi you will be able to:

• Execute any valid JavaScript
• Invoke JavaScript methods from C++
• Expose C++ methods to JavaScript
• Expose C++ objects to JavaScript
• Consume JavaScript objects in C++
• Handle errors with C++ exceptions
• Create any number of Runtimes and Contexts - simultaneously on multiple threads

##Gratuitous Screenshot

The image below shows libjsapi hosting a GTK+ application which emulates enough browser bits to render a funky JavaScript Mandelbrot application ported from https://github.com/cslarsen/mandelbrot-js.

The window on the left is Firefox rendering a Mandelbrot fractal, on the right is the libjsapi application running (mainly) the same JavaScript code.

##Examples:

The simplest thing that could possibly work:

#include <iostream>
#include "libjsapi.h"

int main() {
    // create the context which hosts spidermonkey
    rs::jsapi::Context cx;
    
    // execute a script in the context of the runtime, getting the result
    rs::jsapi::Value result(cx);
    cx.Evaluate("(function(){return 42;})();", result);
    
    // output the result to the console
    std::cout << result << std::endl;
}

Among other things we can expose C++ lambdas (and methods) to JS:

#include <iostream>
#include "libjsapi.h"

int main() {
    // create the context which hosts spidermonkey
    rs::jsapi::Context cx;
    
    // define a function in global scope implemented by a C++ lambda
    rs::jsapi::Global::DefineFunction(cx, "getTheAnswer", 
        [](const std::vector<rs::jsapi::Value>& args, rs::jsapi::Value& result) { 
            result = 42; 
    });
    
    // call the native function from JS
    rs::jsapi::Value result(cx);
    cx.Evaluate("(function(){return getTheAnswer();})();", result);
    
    // output the result to the console
    std::cout << result << std::endl;
}

The wiki contains more background on JSAPI, libjsapi and further examples.

Building

Requires:

• GCC 4.8.1+
• GNU Make
• lcov and Ruby (for test coverage)
• valgrind (for memory analysis)

To build type:

$ make

The first libjsapi build may take a long time to complete since it will invoke a build of SpiderMonkey and GoogleTest. Subsequent builds do not require this step and will be much faster.

To build tests with coverage:

$ make test

To create a coverage report:

$ ./coverage.sh

To create a valgrind report:

$ ./grind.sh

You will find examples in the examples directory. You can build these after building libjsapi by running:

$ cd examples
$ make

If building is slow on your system then you can speed it up by stripping the debugging information from the mozjs library by running ./strip_mozjs.sh.

The wiki contains details on building on different systems.