Cross-context JavaScript function invocation with embedded Google V8

v8-embedder.cpp

#include "v8/libplatform/libplatform.h"
#include "v8/v8.h"
#include <iostream>
#pragma comment(lib, "v8_monolith")

int main() {
    auto platform = v8::platform::NewDefaultPlatform();
    v8::V8::InitializePlatform(platform.get());
    v8::V8::Initialize();

    v8::Isolate::CreateParams params;
    params.array_buffer_allocator = v8::ArrayBuffer::Allocator::NewDefaultAllocator();
    v8::Isolate *isolate = v8::Isolate::New(params);
    v8::Persistent<v8::Function> isArrayBuffer;

    auto const consoleLogCallback = [](auto const& args) {
        std::cout << static_cast<char*>(
            *v8::String::Utf8Value(args.GetIsolate(), args[0])) << std::endl;
    };

    auto const v8StringFromUtf8 = [isolate](char const * const str) {
        return v8::String::NewFromUtf8(isolate, str,
            v8::NewStringType::kNormal).ToLocalChecked();
    };

    auto const runRoutineInNewContext = [&platform, isolate](auto routine) {
        v8::Isolate::Scope isolateScope(isolate);
        v8::HandleScope handleScope(isolate);
        v8::Local<v8::Context> context = v8::Context::New(isolate);
        v8::Context::Scope contextScope(context);
        routine(context);
        while (v8::platform::PumpMessageLoop(platform.get(), isolate));
    };

    auto const getGlobalProperty = [&](auto &context, auto name) {
        return context->Global()->GetRealNamedProperty(
            context, v8StringFromUtf8(name)).ToLocalChecked();
    };

    // --- C o n t e x t  # 1 ---
    runRoutineInNewContext([&](auto &context) {
        getGlobalProperty(context, "console").As<v8::Object>()
            ->Set(context, v8StringFromUtf8("log"),
                v8::Function::New(isolate, consoleLogCallback));
        v8::Script::Compile(context, v8StringFromUtf8(R"JS(
            // (A)
            function isArrayBuffer(x) {
                console.log(x.constructor.toString());        // (1)
                console.log(x.constructor === ArrayBuffer);   // (2)

                let y = new ArrayBuffer();
                console.log(y.constructor.toString());        // (3)
                console.log(y.constructor === ArrayBuffer);   // (4)
            }
        )JS")).ToLocalChecked()->Run(context);
        isArrayBuffer.Reset(isolate,
            getGlobalProperty(context, "isArrayBuffer").As<v8::Function>());
    });

    // --- C o n t e x t  # 2 ---
    runRoutineInNewContext([&](auto &context) {
        context->Global()->Set(context,
            v8StringFromUtf8("isArrayBuffer"),
            v8::Local<v8::Function>::New(isolate, isArrayBuffer));
        v8::Script::Compile(context, v8StringFromUtf8(R"JS(
            // (B)
            isArrayBuffer(new ArrayBuffer());
        )JS")).ToLocalChecked()->Run(context);
    });
    
    //
    // ---- C o n s o l e  O u t p u t ----
    //
    // (1) // function ArrayBuffer() { [native code] }
    // (2) // false
    // (3) // function ArrayBuffer() { [native code] }
    // (4) // true
    //
    
    isolate->Dispose();
    v8::V8::Dispose();
    v8::V8::ShutdownPlatform();
    delete params.array_buffer_allocator;
}