如何在 V8 javascript 引擎中启用和使用 ES6 模块？

Question

我在我的（Windows 桌面）C++ 应用程序中使用嵌入式 V8 引擎。我知道 V8 支持 ES6 模块。我将如何在我的应用程序中激活和使用此功能？

我不希望任何人有一个完整的工作示例来说明它是如何工作的，但是一个高水平的答案将我（和未来的读者）指向正确的方向将完全满足我对这个问题的希望和愿望。

Answer 1

代替 V8 的实际示例（我实际上打算在某个时候写一些），我将在这里写一个。对于一些在野外使用的例子，我推荐 Node.js's implementation, or my own, both using very similar layouts (having been written by the same people). There is also an implementation in D8, V8's CLI debugger.

Local<String> source_text = String::NewFromUtf8(
    isolate, "import 'some thing'; 1 + 1");

ScriptOrigin origin(String::NewFromUtf8("main.mjs"),      // specifier
                    Integer::New(isolate, 0),             // line offset
                    Integer::New(isolate, 0),             // column offset
                    False(isolate),                       // is cross origin
                    Local<Integer>(),                     // script id
                    Local<Value>(),                       // source map URL
                    False(isolate),                       // is opaque
                    False(isolate),                       // is WASM
                    True(isolate));                       // is ES6 module
Context::Scope context_scope(context);
ScriptCompiler::Source source(source_text, origin);
Local<Module> module;
if (!ScriptCompiler::CompileModule(isolate, &source).ToLocal(&module)) {
  // if you have a v8::TryCatch, you should check it here.
  return;
}

// You can resolve import requests ahead of time (useful for async)
for (int i = 0; i < module->GetModuleRequestsLength(); i++) {
  Local<String> specifier = module->GetModuleRequest(i); // "some thing"
}

// or you can resolve them sync in the InstantiateModule callback
module->InstantiateModule(context, [](Local<Context> context, // "main.mjs"
                                      Local<String> specifier, // "some thing"
                                      Local<Module> referrer) {
  return Local<Module>();
});

// setting this callback enables dynamic import
isolate->SetImportModuleDynamicallyCallback([](Local<Context> context,
                                               Local<ScriptOrModule> referrer,
                                               Local<String> specifier) {
  return MaybeLocal<Promise>();
});

// setting this callback enables import.meta
isolate->SetHostInitializeImportMetaObjectCallback([](Local<Context> context,
                                                      Local<Module> module,
                                                      Local<Object> meta) {
  // meta->Set(key, value); you could set import.meta.url here
});

Local<Value> result;
if (module->Evaluate(context).ToLocal(&result)) {
  String::Utf8Value utf8(isolate, result);
  printf("module eval result: %s\n", *utf8);
} else {
  // once again, if you have a v8::TryCatch, use it here.
}

如何在 V8 javascript 引擎中启用和使用 ES6 模块？

How would one enable and use ES6 modules in the V8 javascript engine?

v8

es6-modules

embedded-v8