hello.cpp

#include <cstdio>

#include <jsapi.h>
#include <js/CompilationAndEvaluation.h>
#include <js/SourceText.h>

#include "boilerplate.h"

// This example illustrates the bare minimum you need to do to execute a
// JavaScript program using embedded SpiderMonkey. It does no error handling and
// simply exits if something goes wrong.
//
// See 'boilerplate.cpp' for the parts of this example that are reused in many
// simple embedding examples.
//
// To use the interpreter you need to create a context and a global object, and
// do some setup on both of these. You also need to enter a "realm" (environment
// within one global object) before you can execute code.

static bool ExecuteCodePrintResult(JSContext* cx, const char* code) {
  JS::CompileOptions options(cx);
  options.setFileAndLine("noname", 1);

  JS::SourceText<mozilla::Utf8Unit> source;
  if (!source.init(cx, code, strlen(code), JS::SourceOwnership::Borrowed)) {
    return false;
  }

  JS::RootedValue rval(cx);
  if (!JS::Evaluate(cx, options, source, &rval)) return false;

  // There are many ways to display an arbitrary value as a result. In this
  // case, we know that the value is an ASCII string because of the expression
  // that we executed, so we can just print the string directly.
  printf("%s\n", JS_EncodeStringToASCII(cx, rval.toString()).get());
  return true;
}

static bool HelloExample(JSContext* cx) {
  JS::RootedObject global(cx, boilerplate::CreateGlobal(cx));
  if (!global) {
    return false;
  }

  JSAutoRealm ar(cx, global);

  // The 'js' delimiter is meaningless, but it's useful for marking C++ raw
  // strings semantically.
  return ExecuteCodePrintResult(cx, R"js(
    `hello world, it is ${new Date()}`
  )js");
}

int main(int argc, const char* argv[]) {
  if (!boilerplate::RunExample(HelloExample)) {
    return 1;
  }
  return 0;
}