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promise_js.go
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/
promise_js.go
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//go:build js && wasm
package ego
import (
"fmt"
"sync"
"syscall/js"
)
// AsyncFuncOf returns an async function to be used by JavaScript.
func AsyncFuncOf(fn func(this js.Value, args []js.Value) any) js.Func {
return js.FuncOf(func(this js.Value, args []js.Value) any {
return js.Global().Get("Promise").New(js.FuncOf(func(_ js.Value, _args []js.Value) any {
resolve, reject := _args[0], _args[1]
go func() {
defer func() {
if r := recover(); r != nil {
reject.Invoke(js.Global().Get("Error").New(fmt.Sprintf("%+v", r)))
}
}()
x := fn(this, args)
switch x := x.(type) {
case []byte:
resolve.Invoke(BytesToUint8Array(x))
default:
resolve.Invoke(x)
}
}()
return nil
}))
})
}
// Awaits a promise to be resolved and returned synchronously or rejected as an error.
func Await(v js.Value) (ret js.Value, err error) {
defer func() {
if r := recover(); r != nil {
err = fmt.Errorf("%+v", r)
}
}()
if !(IsObject(v) && IsFunction(v.Get("then"))) {
ret = v
return
}
var wg sync.WaitGroup
wg.Add(1)
v.Call("then", js.FuncOf(func(this js.Value, args []js.Value) any {
ret = args[0]
wg.Done()
return nil
}), js.FuncOf(func(this js.Value, args []js.Value) any {
err = fmt.Errorf("%+v", js.Global().Call("String", args[0]))
wg.Done()
return nil
}))
wg.Wait()
return
}