Begin work in semi-standardized js_wasm32 target

core/fmt/fmt_js.odin

@@ -0,0 +1,44 @@
+//+build js
+package fmt
+
+import "core:io"
+
+foreign import "odin_env"
+
+@(private="file")
+foreign odin_env {
+	write :: proc "c" (fd: u32, p: []byte) ---
+}
+
+@(private="file")
+write_vtable := &io.Stream_VTable{
+	impl_write = proc(s: io.Stream, p: []byte) -> (n: int, err: io.Error) {
+		fd := u32(uintptr(s.stream_data))
+		write(fd, p)
+		return len(p), nil
+	},	
+}
+
+@(private="file")
+stdout := io.Writer{
+	stream = {
+		stream_vtable = write_vtable,
+		stream_data = rawptr(uintptr(1)),
+	},
+}
+@(private="file")
+stderr := io.Writer{
+	stream = {
+		stream_vtable = write_vtable,
+		stream_data = rawptr(uintptr(2)),
+	},
+}
+
+// print* procedures return the number of bytes written
+print   :: proc(args: ..any, sep := " ") -> int { return wprint(w=stdout, args=args, sep=sep) }
+println :: proc(args: ..any, sep := " ") -> int { return wprintln(w=stdout, args=args, sep=sep) }
+printf  :: proc(fmt: string, args: ..any) -> int { return wprintf(stdout, fmt, ..args) }
+
+eprint   :: proc(args: ..any, sep := " ") -> int { return wprint(w=stderr, args=args, sep=sep) }
+eprintln :: proc(args: ..any, sep := " ") -> int { return wprintln(w=stderr, args=args, sep=sep) }
+eprintf  :: proc(fmt: string, args: ..any) -> int { return wprintf(stderr, fmt, ..args) }

core/fmt/fmt_os.odin

@@ -1,4 +1,4 @@
-//+build !freestanding
+//+build !freestanding !js
 package fmt
 
 import "core:runtime"