reorg: move JS ops implementations to cli/js/ops/, part 3 (#4302)

Following JS ops were moved to separate files in cli/js/ops directory:
- net
- tls
- fs

cli/js/ops/fs/read_dir.ts

@@ -0,0 +1,37 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import { sendSync, sendAsync } from "../dispatch_json.ts";
+import { FileInfo, FileInfoImpl } from "../../file_info.ts";
+import { StatResponse } from "./stat.ts";
+
+interface ReadDirResponse {
+  entries: StatResponse[];
+}
+
+function res(response: ReadDirResponse): FileInfo[] {
+  return response.entries.map(
+    (statRes: StatResponse): FileInfo => {
+      return new FileInfoImpl(statRes);
+    }
+  );
+}
+
+/** Synchronously reads the directory given by `path` and returns an array of
+ * `Deno.FileInfo`.
+ *
+ *       const files = Deno.readdirSync("/");
+ *
+ * Requires `allow-read` permission. */
+export function readdirSync(path: string): FileInfo[] {
+  return res(sendSync("op_read_dir", { path }));
+}
+
+/** UNSTABLE: Maybe need to return an `AsyncIterable`.
+ *
+ * Reads the directory given by `path` and resolves to an array of `Deno.FileInfo`.
+ *
+ *       const files = await Deno.readdir("/");
+ *
+ * Requires `allow-read` permission. */
+export async function readdir(path: string): Promise<FileInfo[]> {
+  return res(await sendAsync("op_read_dir", { path }));
+}