Full hasher object with promises

objtest.go

package main

//go:generate gopherjs build --minify

import (
	"crypto/sha256"
	"errors"

	"github.com/gopherjs/gopherjs/js"
	"github.com/miratronix/jopher"
)

func main() {
	js.Module.Get("exports").Set("newHasher", newHasher)
}

type Hasher struct {
	*js.Object
	S    string                          `js:"s"`
	Hash func(...interface{}) *js.Object `js:"hash"`
}

func newHasher(s string) *js.Object {
	h := Hasher{Object: js.Global.Get("Object").New()}
	h.S = s
	h.Hash = jopher.Promisify(h.hash)
	return h.Object
}

func (h *Hasher) hash() ([]byte, error) {
	if h.S == "" {
		return nil, errors.New("hash of an empty string")
	}

	r := sha256.New()
	_, err := r.Write([]byte(h.S))
	if err != nil {
		return nil, err
	}

	return r.Sum(nil), nil
}