Notes from the JSI Consulting Session

private-jsi-consulting.cpp

/**
 * jsi::Value
 *   - .asNumber() -> double
 *   - .asBoolean() -> bool
 *   - jsi::Value::undefined()
 *   - jsi::Value::null()
 *   - jsi::String
 *   - jsi::Symbol
 *   - jsi::Object
 *     - jsi::HostObject<T>
 *     - jsi::Function
 *       - jsi::HostFunction
 *     - jsi::Array
 *     - jsi::ArrayBuffer
 */




jsi::Runtime& runtime; // TODO: Get actual runtime reference

// create a number
auto num = jsi::Value(42);
// create string
auto str = jsi::String::createFromUtf8("hello!", runtime);

// create an object
auto obj = jsi::Object(runtime);
obj.setProperty(runtime, "someNumber", num);
obj.setProperty(runtime, "someString", str);

// get a property from an object
jsi::Value num2 = obj.getProperty(runtime, "someNumber");

// unboxing
bool isNumber = num2.isNumber(runtime);
if (isNumber) {
  double actualNumber = num2.asNumber();
}

// object unboxing
bool isObject = num2.isObject(runtime);
if (isObject) {
  jsi::Object obj = num2.asObject(runtime);
  bool isFunc = obj.isFunction();
}

// create a host-function
auto sayHelloWorld = [](jsi::Runtime& runtime,
                        jsi::Value& thisValue,
                        jsi::Value* arguments,
                        size_t size) -> jsi::Value {

  return jsi::Value::undefined();
};
auto func = jsi::Function::createFunctionFromHostFunction(
  jsi::PropNameID::createPropNameIDFromString(runtime, "sayHelloWorld"),
  std::move(sayHelloWorld),
  0);

// call a (host)-function
func.call(runtime);

// inject any jsi::Value into the global namespace (JS world)
runtime.global().setProperty(runtime, "___sayHelloWorld", func);


// get any constructor
auto newPromise = runtime.global().getPropertyAsFunction(runtime, "Promise");
auto promise = newPromise.callAsConstructor(runtime, /* (resolve, reject) => void */);
return promise;


// JS
global.___sayHelloWorld()