This patch is a proposal for a new introduction, which I find better: It exposes the problem, and explains the need for gowasmer.

By the way, good job with the project!

question

wasm

I build the code to wasm file.

package main

import (
	"syscall/js"

	"github.com/mattn/gowasmer/wasmutil"
)

func Add(a, b int) int {
	return a + b
}

func String(a string) string {
	println(a)
	return a
}

func MultiString(a, b string) string {
	return a + b
}

func main() {
	c := make(chan struct{})
	js.Global().Set("String", js.FuncOf(wasmutil.Wrap(String)))
	js.Global().Set("Add", js.FuncOf(wasmutil.Wrap(Add)))
	js.Global().Set("MultiString", js.FuncOf(wasmutil.Wrap(MultiString)))
	<-c
}

golang code

go run the code. but the function add in wasm is ok, but String and MultiString response emtpy string ?

package main

import (
	"fmt"
	"io/ioutil"
	"log"

	gowasmer "github.com/mattn/gowasmer"
)

func main() {
	b, err := ioutil.ReadFile("wasm-example")
	if err != nil {
		log.Fatal(err)
	}

	inst, err := gowasmer.NewInstance(b)
	if err != nil {
		log.Fatal(err)
	}

	m := inst.Get("Add")
	r := m.(func([]interface{}) interface{})([]interface{}{1, 3})
	fmt.Printf("1 + 3 = %v\n", r)

	m = inst.Get("String")
	r = m.(func([]interface{}) interface{})([]interface{}{"haha"})
	fmt.Printf("String = %v\n", r)

	m = inst.Get("MultiString")
	r = m.(func([]interface{}) interface{})([]interface{}{"aaa", "bbb"})
	fmt.Printf("MultiString = %v\n", r)
}

run stdout:

1 + 3 = 4

String =
MultiString = 

please provide more example, thank u.

😁

I add some code in example like bellow:

package main

import (
	"encoding/json"
	"github.com/mattn/gowasmer/wasmutil"
	"syscall/js"
)

func Add(a, b int) int {
	json.Marshal(123)
	//or time.Now()
	//or fmt.Println()
	return a + b
}

func main() {
	c := make(chan struct{})
	js.Global().Set("Add", js.FuncOf(wasmutil.Wrap(Add)))
	<-c
}

When I run the example , it panics:

panic: syscall/js: call of Value.Get on undefined

goroutine 1 [running]:
syscall/js.Value.Get({{}, 0x0, 0x0}, {0x22f97, 0x9})
/home/wanghh/workspace/go1.17.7/src/syscall/js/js.go:299 +0xc
syscall.init()
/home/wanghh/workspace/go1.17.7/src/syscall/fs_js.go:21 +0x12

Process finished with the exit code 2

So, how do I support 'json.Marshal' 'time.now' 'fmt.xxx' in wasm writen in go ?