how to get a resolve value in a promise?

[czz362100]

hey team, i have some confusions in these code

vm := goja.New()
	promise, err := vm.RunString(`
			async function sum(a, b) {
    			return a+b;
			}
	`)
	if err != nil {
		panic(err)
	}
	add, ok := goja.AssertFunction(vm.Get("sum"))
	if !ok {
		panic("not a function")
	}

	value, _ := add(goja.Undefined(), vm.ToValue(40), vm.ToValue(2))
	return value

in this example, the sum Function return a [object, Promise], but i want to get a Resolved value, please tell me how do i?

[shiroyk]

Export to promise

func main() {
	vm := goja.New()
	_, err := vm.RunString(`
			async function sum(a, b) {
    			return a+b;
			}
	`)
	if err != nil {
		panic(err)
	}
	add, ok := goja.AssertFunction(vm.Get("sum"))
	if !ok {
		panic("not a function")
	}

	value, _ := add(goja.Undefined(), vm.ToValue(40), vm.ToValue(2))

	var result any
	if p, ok := value.Export().(*goja.Promise); ok {
		switch p.State() {
		case goja.PromiseStateRejected:
			panic(p.Result().String())
		case goja.PromiseStateFulfilled:
			result = p.Result().Export()
		default:
			panic("unexpected promise state pending")
		}
	}

	fmt.Println(result)
}

[cjf621]

Export to promise

func main() {
	vm := goja.New()
	_, err := vm.RunString(`
			async function sum(a, b) {
    			return a+b;
			}
	`)
	if err != nil {
		panic(err)
	}
	add, ok := goja.AssertFunction(vm.Get("sum"))
	if !ok {
		panic("not a function")
	}

	value, _ := add(goja.Undefined(), vm.ToValue(40), vm.ToValue(2))

	var result any
	if p, ok := value.Export().(*goja.Promise); ok {
		switch p.State() {
		case goja.PromiseStateRejected:
			panic(p.Result().String())
		case goja.PromiseStateFulfilled:
			result = p.Result().Export()
		default:
			panic("unexpected promise state pending")
		}
	}

	fmt.Println(result)
}

I would like to ask a question，the promise is async，so in goja in golang it is sync？If the execution is not completed when the results are obtained，it is true？

[shiroyk]

Export to promise

func main() {
	vm := goja.New()
	_, err := vm.RunString(`
			async function sum(a, b) {
    			return a+b;
			}
	`)
	if err != nil {
		panic(err)
	}
	add, ok := goja.AssertFunction(vm.Get("sum"))
	if !ok {
		panic("not a function")
	}

	value, _ := add(goja.Undefined(), vm.ToValue(40), vm.ToValue(2))

	var result any
	if p, ok := value.Export().(*goja.Promise); ok {
		switch p.State() {
		case goja.PromiseStateRejected:
			panic(p.Result().String())
		case goja.PromiseStateFulfilled:
			result = p.Result().Export()
		default:
			panic("unexpected promise state pending")
		}
	}

	fmt.Println(result)
}

I would like to ask a question，the promise is async，so in goja in golang it is sync？If the execution is not completed when the results are obtained，it is true？

It's async, you can also see

goja/builtin_promise.go

Lines 592 to 611 in 28ee0ee

	// NewPromise creates and returns a Promise and resolving functions for it.
	//
	// WARNING: The returned values are not goroutine-safe and must not be called in parallel with VM running.
	// In order to make use of this method you need an event loop such as the one in goja_nodejs (https://github.com/dop251/goja_nodejs)
	// where it can be used like this:
	//
	// loop := NewEventLoop()
	// loop.Start()
	// defer loop.Stop()
	// loop.RunOnLoop(func(vm *goja.Runtime) {
	// p, resolve, _ := vm.NewPromise()
	// vm.Set("p", p)
	// go func() {
	// time.Sleep(500 * time.Millisecond) // or perform any other blocking operation
	// loop.RunOnLoop(func(*goja.Runtime) { // resolve() must be called on the loop, cannot call it here
	// resolve(result)
	// })
	// }()
	// }
	func (r *Runtime) NewPromise() (promise *Promise, resolve func(result interface{}), reject func(reason interface{})) {