golang exists_js 代码
文件路径：/src/os/exec/internal/fdtest/exists_js.go
/ Copyright 2021 The Go Authors. All rights reserved.
/ Use of this source code is governed by a BSD-style
/ license that can be found in the LICENSE file.
/go:build js
package fdtest
import (
"syscall"
)
/ Exists returns true if fd is a valid file descriptor.
func Exists(fd uintptr) bool {
var s syscall.Stat_t
err := syscall.Fstat(int(fd), &s)
return err != syscall.EBADF
}