refactor: add more typing info and upgrade prettier (#3725)

This upgrades prettier to 2.2.0 to gain support for TypeScript's new type-only-imports feature.
2026-04-30 03:00:39 -04:00 · 2020-12-11 03:19:20 -08:00
parent 81c1f4e819
commit d1bfe40dbb
10 changed files with 483 additions and 476 deletions
--- a/lib/client.ts
+++ b/lib/client.ts
@@ -1,10 +1,9 @@
 import { Decoder, Encoder, Packet, PacketType } from "socket.io-parser";
 import debugModule = require("debug");
-import { IncomingMessage } from "http";
-import { Server } from "./index";
-import { Socket } from "./socket";
-import { SocketId } from "socket.io-adapter";
-import { ParentNamespace } from "./parent-namespace";
+import type { IncomingMessage } from "http";
+import type { Namespace, Server } from "./index";
+import type { Socket } from "./socket";
+import type { SocketId } from "socket.io-adapter";

 const debug = debugModule("socket.io:client");

@@ -17,16 +16,16 @@ export class Client {
  private readonly decoder: Decoder;
  private sockets: Map<SocketId, Socket> = new Map();
  private nsps: Map<string, Socket> = new Map();
-  private connectTimeout: NodeJS.Timeout;
+  private connectTimeout?: NodeJS.Timeout;

  /**
   * Client constructor.
   *
-   * @param {Server} server instance
-   * @param {Socket} conn
+   * @param server instance
+   * @param conn
   * @package
   */
-  constructor(server: Server, conn) {
+  constructor(server: Server, conn: Socket) {
    this.server = server;
    this.conn = conn;
    this.encoder = server.encoder;
@@ -84,27 +83,31 @@ export class Client {
      return this.doConnect(name, auth);
    }

-    this.server._checkNamespace(name, auth, (dynamicNsp: ParentNamespace) => {
-      if (dynamicNsp) {
-        debug("dynamic namespace %s was created", dynamicNsp.name);
-        this.doConnect(name, auth);
-      } else {
-        debug("creation of namespace %s was denied", name);
-        this._packet({
-          type: PacketType.CONNECT_ERROR,
-          nsp: name,
-          data: {
-            message: "Invalid namespace"
-          }
-        });
+    this.server._checkNamespace(
+      name,
+      auth,
+      (dynamicNspName: Namespace | false) => {
+        if (dynamicNspName) {
+          debug("dynamic namespace %s was created", dynamicNspName);
+          this.doConnect(name, auth);
+        } else {
+          debug("creation of namespace %s was denied", name);
+          this._packet({
+            type: PacketType.CONNECT_ERROR,
+            nsp: name,
+            data: {
+              message: "Invalid namespace",
+            },
+          });
+        }
      }
-    });
+    );
  }

  /**
   * Connects a client to a namespace.
   *
-   * @param {String} name - the namespace
+   * @param name - the namespace
   * @param {Object} auth - the auth parameters
   *
   * @private
@@ -112,7 +115,7 @@ export class Client {
  private doConnect(name: string, auth: object) {
    if (this.connectTimeout) {
      clearTimeout(this.connectTimeout);
-      this.connectTimeout = null;
+      this.connectTimeout = undefined;
    }
    const nsp = this.server.of(name);

@@ -142,7 +145,7 @@ export class Client {
   */
  _remove(socket: Socket) {
    if (this.sockets.has(socket.id)) {
-      const nsp = this.sockets.get(socket.id).nsp.name;
+      const nsp = this.sockets.get(socket.id)!.nsp.name;
      this.sockets.delete(socket.id);
      this.nsps.delete(nsp);
    } else {
@@ -221,7 +224,7 @@ export class Client {
    } else {
      const socket = this.nsps.get(packet.nsp);
      if (socket) {
-        process.nextTick(function() {
+        process.nextTick(function () {
          socket._onpacket(packet);
        });
      } else {
--- a/lib/index.ts
+++ b/lib/index.ts
@@ -11,11 +11,11 @@ import { ExtendedError, Namespace } from "./namespace";
 import { ParentNamespace } from "./parent-namespace";
 import { Adapter, Room, SocketId } from "socket.io-adapter";
 import * as parser from "socket.io-parser";
-import { Encoder } from "socket.io-parser";
+import type { Encoder } from "socket.io-parser";
 import debugModule from "debug";
 import { Socket } from "./socket";
-import { CookieSerializeOptions } from "cookie";
-import { CorsOptions } from "cors";
+import type { CookieSerializeOptions } from "cookie";
+import type { CorsOptions } from "cors";

 const debug = debugModule("socket.io:server");

@@ -23,6 +23,11 @@ const clientVersion = require("../package.json").version;
 const dotMapRegex = /\.map/;

 type Transport = "polling" | "websocket";
+type ParentNspNameMatchFn = (
+  name: string,
+  query: object,
+  fn: (err: Error | null, success: boolean) => void
+) => void;

 interface EngineOptions {
  /**
@@ -149,7 +154,7 @@ export class Server extends EventEmitter {
  public readonly sockets: Namespace;

  /** @private */
-  readonly _parser;
+  readonly _parser: typeof parser;
  /** @private */
  readonly encoder: Encoder;

@@ -157,17 +162,8 @@ export class Server extends EventEmitter {
   * @private
   */
  _nsps: Map<string, Namespace> = new Map();
-  private parentNsps: Map<
-    | string
-    | RegExp
-    | ((
-        name: string,
-        query: object,
-        fn: (err: Error, success: boolean) => void
-      ) => void),
-    ParentNamespace
-  > = new Map();
-  private _adapter: any;
+  private parentNsps: Map<ParentNspNameMatchFn, ParentNamespace> = new Map();
+  private _adapter?: typeof Adapter;
  private _serveClient: boolean;
  private opts: Partial<EngineOptions>;
  private eio;
@@ -184,18 +180,24 @@ export class Server extends EventEmitter {
  /**
   * Server constructor.
   *
-   * @param {http.Server|Number|Object} srv http server, port or options
-   * @param {Object} [opts]
+   * @param srv http server, port, or options
+   * @param [opts]
   * @public
   */
  constructor(opts?: Partial<ServerOptions>);
-  constructor(srv: http.Server, opts?: Partial<ServerOptions>);
-  constructor(srv: number, opts?: Partial<ServerOptions>);
-  constructor(srv?: any, opts: Partial<ServerOptions> = {}) {
+  constructor(srv?: http.Server | number, opts?: Partial<ServerOptions>);
+  constructor(
+    srv: undefined | Partial<ServerOptions> | http.Server | number,
+    opts: Partial<ServerOptions> = {}
+  ) {
    super();
-    if ("object" == typeof srv && srv instanceof Object && !srv.listen) {
-      opts = srv;
-      srv = null;
+    if (
+      "object" === typeof srv &&
+      srv instanceof Object &&
+      !(srv as Partial<http.Server>).listen
+    ) {
+      opts = srv as Partial<ServerOptions>;
+      srv = undefined;
    }
    this.path(opts.path || "/socket.io");
    this.connectTimeout(opts.connectTimeout || 45000);
@@ -205,44 +207,44 @@ export class Server extends EventEmitter {
    this.adapter(opts.adapter || Adapter);
    this.sockets = this.of("/");
    this.opts = opts;
-    if (srv) this.attach(srv);
+    if (srv) this.attach(srv as http.Server);
  }

  /**
   * Sets/gets whether client code is being served.
   *
-   * @param {Boolean} v - whether to serve client code
-   * @return {Server|Boolean} self when setting or value when getting
+   * @param v - whether to serve client code
+   * @return self when setting or value when getting
   * @public
   */
  public serveClient(v: boolean): Server;
  public serveClient(): boolean;
  public serveClient(v?: boolean): Server | boolean {
    if (!arguments.length) return this._serveClient;
-    this._serveClient = v;
+    this._serveClient = v!;
    return this;
  }

  /**
   * Executes the middleware for an incoming namespace not already created on the server.
   *
-   * @param {String} name - name of incoming namespace
+   * @param name - name of incoming namespace
   * @param {Object} auth - the auth parameters
-   * @param {Function} fn - callback
+   * @param fn - callback
   *
   * @private
   */
  _checkNamespace(
    name: string,
    auth: object,
-    fn: (nsp: Namespace | boolean) => void
+    fn: (nsp: Namespace | false) => void
  ) {
    if (this.parentNsps.size === 0) return fn(false);

    const keysIterator = this.parentNsps.keys();

    const run = () => {
-      let nextFn = keysIterator.next();
+      const nextFn = keysIterator.next();
      if (nextFn.done) {
        return fn(false);
      }
@@ -250,7 +252,7 @@ export class Server extends EventEmitter {
        if (err || !allow) {
          run();
        } else {
-          fn(this.parentNsps.get(nextFn.value).createChild(name));
+          fn(this.parentNsps.get(nextFn.value)!.createChild(name));
        }
      });
    };
@@ -270,7 +272,7 @@ export class Server extends EventEmitter {
  public path(v?: string): Server | string {
    if (!arguments.length) return this._path;

-    this._path = v.replace(/\/$/, "");
+    this._path = v!.replace(/\/$/, "");

    const escapedPath = this._path.replace(/[-\/\\^$*+?.()|[\]{}]/g, "\\$&");
    this.clientPathRegex = new RegExp(
@@ -297,13 +299,13 @@ export class Server extends EventEmitter {
  /**
   * Sets the adapter for rooms.
   *
-   * @param {Adapter} v pathname
-   * @return {Server|Adapter} self when setting or value when getting
+   * @param v pathname
+   * @return self when setting or value when getting
   * @public
   */
-  public adapter(): any;
-  public adapter(v: any);
-  public adapter(v?): Server | any {
+  public adapter(): typeof Adapter | undefined;
+  public adapter(v: typeof Adapter): Server;
+  public adapter(v?: typeof Adapter): typeof Adapter | undefined | Server {
    if (!arguments.length) return this._adapter;
    this._adapter = v;
    for (const nsp of this._nsps.values()) {
@@ -315,28 +317,30 @@ export class Server extends EventEmitter {
  /**
   * Attaches socket.io to a server or port.
   *
-   * @param {http.Server|Number} srv - server or port
-   * @param {Object} opts - options passed to engine.io
-   * @return {Server} self
+   * @param srv - server or port
+   * @param opts - options passed to engine.io
+   * @return self
   * @public
   */
-  public listen(srv: http.Server, opts?: Partial<ServerOptions>): Server;
-  public listen(srv: number, opts?: Partial<ServerOptions>): Server;
-  public listen(srv: any, opts: Partial<ServerOptions> = {}): Server {
+  public listen(
+    srv: http.Server | number,
+    opts: Partial<ServerOptions> = {}
+  ): Server {
    return this.attach(srv, opts);
  }

  /**
   * Attaches socket.io to a server or port.
   *
-   * @param {http.Server|Number} srv - server or port
-   * @param {Object} opts - options passed to engine.io
-   * @return {Server} self
+   * @param srv - server or port
+   * @param opts - options passed to engine.io
+   * @return self
   * @public
   */
-  public attach(srv: http.Server, opts?: Partial<ServerOptions>): Server;
-  public attach(port: number, opts?: Partial<ServerOptions>): Server;
-  public attach(srv: any, opts: Partial<ServerOptions> = {}): Server {
+  public attach(
+    srv: http.Server | number,
+    opts: Partial<ServerOptions> = {}
+  ): Server {
    if ("function" == typeof srv) {
      const msg =
        "You are trying to attach socket.io to an express " +
@@ -394,10 +398,10 @@ export class Server extends EventEmitter {
  /**
   * Attaches the static file serving.
   *
-   * @param {Function|http.Server} srv http server
+   * @param srv http server
   * @private
   */
-  private attachServe(srv) {
+  private attachServe(srv: http.Server) {
    debug("attaching client serving req handler");

    const evs = srv.listeners("request").slice(0);
@@ -416,12 +420,12 @@ export class Server extends EventEmitter {
  /**
   * Handles a request serving of client source and map
   *
-   * @param {http.IncomingMessage} req
-   * @param {http.ServerResponse} res
+   * @param req
+   * @param res
   * @private
   */
  private serve(req: http.IncomingMessage, res: http.ServerResponse) {
-    const filename = req.url.replace(this._path, "");
+    const filename = req.url!.replace(this._path, "");
    const isMap = dotMapRegex.test(filename);
    const type = isMap ? "map" : "source";

@@ -470,7 +474,7 @@ export class Server extends EventEmitter {
    );
    const encoding = accepts(req).encodings(["br", "gzip", "deflate"]);

-    const onError = err => {
+    const onError = (err: NodeJS.ErrnoException | null) => {
      if (err) {
        res.end();
      }
@@ -500,7 +504,7 @@ export class Server extends EventEmitter {
   * Binds socket.io to an engine.io instance.
   *
   * @param {engine.Server} engine engine.io (or compatible) server
-   * @return {Server} self
+   * @return self
   * @public
   */
  public bind(engine): Server {
@@ -513,7 +517,7 @@ export class Server extends EventEmitter {
   * Called with each incoming transport connection.
   *
   * @param {engine.Socket} conn
-   * @return {Server} self
+   * @return self
   * @private
   */
  private onconnection(conn): Server {
@@ -526,18 +530,11 @@ export class Server extends EventEmitter {
   * Looks up a namespace.
   *
   * @param {String|RegExp|Function} name nsp name
-   * @param {Function} [fn] optional, nsp `connection` ev handler
+   * @param [fn] optional, nsp `connection` ev handler
   * @public
   */
  public of(
-    name:
-      | string
-      | RegExp
-      | ((
-          name: string,
-          query: object,
-          fn: (err: Error, success: boolean) => void
-        ) => void),
+    name: string | RegExp | ParentNspNameMatchFn,
    fn?: (socket: Socket) => void
  ) {
    if (typeof name === "function" || name instanceof RegExp) {
@@ -573,7 +570,7 @@ export class Server extends EventEmitter {
  /**
   * Closes server connection
   *
-   * @param {Function} [fn] optional, called as `fn([err])` on error OR all conns closed
+   * @param [fn] optional, called as `fn([err])` on error OR all conns closed
   * @public
   */
  public close(fn?: (err?: Error) => void): void {
@@ -593,7 +590,7 @@ export class Server extends EventEmitter {
  /**
   * Sets up namespace middleware.
   *
-   * @return {Server} self
+   * @return self
   * @public
   */
  public use(
@@ -606,8 +603,8 @@ export class Server extends EventEmitter {
  /**
   * Targets a room when emitting.
   *
-   * @param {String} name
-   * @return {Server} self
+   * @param name
+   * @return self
   * @public
   */
  public to(name: Room): Server {
@@ -618,8 +615,8 @@ export class Server extends EventEmitter {
  /**
   * Targets a room when emitting.
   *
-   * @param {String} name
-   * @return {Server} self
+   * @param name
+   * @return self
   * @public
   */
  public in(name: Room): Server {
@@ -630,24 +627,22 @@ export class Server extends EventEmitter {
  /**
   * Sends a `message` event to all clients.
   *
-   * @return {Server} self
+   * @return self
   * @public
   */
-  public send(...args): Server {
-    args.unshift("message");
-    this.sockets.emit.apply(this.sockets, args);
+  public send(...args: readonly any[]): Server {
+    this.sockets.emit("message", ...args);
    return this;
  }

  /**
   * Sends a `message` event to all clients.
   *
-   * @return {Server} self
+   * @return self
   * @public
   */
-  public write(...args): Server {
-    args.unshift("message");
-    this.sockets.emit.apply(this.sockets, args);
+  public write(...args: readonly any[]): Server {
+    this.sockets.emit("message", ...args);
    return this;
  }

@@ -663,8 +658,8 @@ export class Server extends EventEmitter {
  /**
   * Sets the compress flag.
   *
-   * @param {Boolean} compress - if `true`, compresses the sending data
-   * @return {Server} self
+   * @param compress - if `true`, compresses the sending data
+   * @return self
   * @public
   */
  public compress(compress: boolean): Server {
@@ -677,7 +672,7 @@ export class Server extends EventEmitter {
   * receive messages (because of network slowness or other issues, or because they’re connected through long polling
   * and is in the middle of a request-response cycle).
   *
-   * @return {Server} self
+   * @return self
   * @public
   */
  public get volatile(): Server {
@@ -688,7 +683,7 @@ export class Server extends EventEmitter {
  /**
   * Sets a modifier for a subsequent event emission that the event data will only be broadcast to the current node.
   *
-   * @return {Server} self
+   * @return self
   * @public
   */
  public get local(): Server {
@@ -701,14 +696,14 @@ export class Server extends EventEmitter {
 * Expose main namespace (/).
 */

-const emitterMethods = Object.keys(EventEmitter.prototype).filter(function(
+const emitterMethods = Object.keys(EventEmitter.prototype).filter(function (
  key
 ) {
  return typeof EventEmitter.prototype[key] === "function";
 });

-emitterMethods.forEach(function(fn) {
-  Server.prototype[fn] = function() {
+emitterMethods.forEach(function (fn) {
+  Server.prototype[fn] = function () {
    return this.sockets[fn].apply(this.sockets, arguments);
  };
 });
--- a/lib/namespace.ts
+++ b/lib/namespace.ts
@@ -1,10 +1,10 @@
 import { Socket, RESERVED_EVENTS } from "./socket";
-import { Server } from "./index";
-import { Client } from "./client";
+import type { Server } from "./index";
+import type { Client } from "./client";
 import { EventEmitter } from "events";
 import { PacketType } from "socket.io-parser";
 import debugModule from "debug";
-import { Adapter, Room, SocketId } from "socket.io-adapter";
+import type { Adapter, Room, SocketId } from "socket.io-adapter";

 const debug = debugModule("socket.io:namespace");

@@ -23,7 +23,7 @@ export class Namespace extends EventEmitter {

  /** @private */
  _fns: Array<
-    (socket: Socket, next: (err: ExtendedError) => void) => void
+    (socket: Socket, next: (err?: ExtendedError) => void) => void
  > = [];

  /** @private */
@@ -38,8 +38,8 @@ export class Namespace extends EventEmitter {
  /**
   * Namespace constructor.
   *
-   * @param {Server} server instance
-   * @param {string} name
+   * @param server instance
+   * @param name
   */
  constructor(server: Server, name: string) {
    super();
@@ -56,13 +56,13 @@ export class Namespace extends EventEmitter {
   * @private
   */
  _initAdapter(): void {
-    this.adapter = new (this.server.adapter())(this);
+    this.adapter = new (this.server.adapter()!)(this);
  }

  /**
   * Sets up namespace middleware.
   *
-   * @return {Namespace} self
+   * @return self
   * @public
   */
  public use(
@@ -75,16 +75,16 @@ export class Namespace extends EventEmitter {
  /**
   * Executes the middleware for an incoming client.
   *
-   * @param {Socket} socket - the socket that will get added
-   * @param {Function} fn - last fn call in the middleware
+   * @param socket - the socket that will get added
+   * @param fn - last fn call in the middleware
   * @private
   */
-  private run(socket: Socket, fn: (err: ExtendedError) => void) {
+  private run(socket: Socket, fn: (err: ExtendedError | null) => void) {
    const fns = this._fns.slice(0);
    if (!fns.length) return fn(null);

-    function run(i) {
-      fns[i](socket, function(err) {
+    function run(i: number) {
+      fns[i](socket, function (err) {
        // upon error, short-circuit
        if (err) return fn(err);

@@ -102,8 +102,8 @@ export class Namespace extends EventEmitter {
  /**
   * Targets a room when emitting.
   *
-   * @param {String} name
-   * @return {Namespace} self
+   * @param name
+   * @return self
   * @public
   */
  public to(name: Room): Namespace {
@@ -114,8 +114,8 @@ export class Namespace extends EventEmitter {
  /**
   * Targets a room when emitting.
   *
-   * @param {String} name
-   * @return {Namespace} self
+   * @param name
+   * @return self
   * @public
   */
  public in(name: Room): Namespace {
@@ -132,13 +132,13 @@ export class Namespace extends EventEmitter {
  _add(client: Client, query, fn?: () => void): Socket {
    debug("adding socket to nsp %s", this.name);
    const socket = new Socket(this, client, query);
-    this.run(socket, err => {
+    this.run(socket, (err) => {
      process.nextTick(() => {
        if ("open" == client.conn.readyState) {
          if (err)
            return socket._error({
              message: err.message,
-              data: err.data
+              data: err.data,
            });

          // track socket
@@ -178,10 +178,10 @@ export class Namespace extends EventEmitter {
  /**
   * Emits to all clients.
   *
-   * @return {Boolean} Always true
+   * @return Always true
   * @public
   */
-  public emit(ev: string, ...args: any[]): boolean {
+  public emit(ev: string | Symbol, ...args: any[]): true {
    if (RESERVED_EVENTS.has(ev)) {
      throw new Error(`"${ev}" is a reserved event name`);
    }
@@ -189,7 +189,7 @@ export class Namespace extends EventEmitter {
    args.unshift(ev);
    const packet = {
      type: PacketType.EVENT,
-      data: args
+      data: args,
    };

    if ("function" == typeof args[args.length - 1]) {
@@ -205,7 +205,7 @@ export class Namespace extends EventEmitter {

    this.adapter.broadcast(packet, {
      rooms: rooms,
-      flags: flags
+      flags: flags,
    });

    return true;
@@ -214,31 +214,29 @@ export class Namespace extends EventEmitter {
  /**
   * Sends a `message` event to all clients.
   *
-   * @return {Namespace} self
+   * @return self
   * @public
   */
-  public send(...args): Namespace {
-    args.unshift("message");
-    this.emit.apply(this, args);
+  public send(...args: readonly any[]): Namespace {
+    this.emit("message", ...args);
    return this;
  }

  /**
   * Sends a `message` event to all clients.
   *
-   * @return {Namespace} self
+   * @return self
   * @public
   */
-  public write(...args): Namespace {
-    args.unshift("message");
-    this.emit.apply(this, args);
+  public write(...args: readonly any[]): Namespace {
+    this.emit("message", ...args);
    return this;
  }

  /**
   * Gets a list of clients.
   *
-   * @return {Namespace} self
+   * @return self
   * @public
   */
  public allSockets(): Promise<Set<SocketId>> {
@@ -255,8 +253,8 @@ export class Namespace extends EventEmitter {
  /**
   * Sets the compress flag.
   *
-   * @param {Boolean} compress - if `true`, compresses the sending data
-   * @return {Namespace} self
+   * @param compress - if `true`, compresses the sending data
+   * @return self
   * @public
   */
  public compress(compress: boolean): Namespace {
@@ -269,7 +267,7 @@ export class Namespace extends EventEmitter {
   * receive messages (because of network slowness or other issues, or because they’re connected through long polling
   * and is in the middle of a request-response cycle).
   *
-   * @return {Namespace} self
+   * @return self
   * @public
   */
  public get volatile(): Namespace {
@@ -280,7 +278,7 @@ export class Namespace extends EventEmitter {
  /**
   * Sets a modifier for a subsequent event emission that the event data will only be broadcast to the current node.
   *
-   * @return {Namespace} self
+   * @return self
   * @public
   */
  public get local(): Namespace {
--- a/lib/parent-namespace.ts
+++ b/lib/parent-namespace.ts
@@ -1,20 +1,26 @@
 import { Namespace } from "./namespace";
+import type { Server } from "./index";

 export class ParentNamespace extends Namespace {
  private static count: number = 0;
  private children: Set<Namespace> = new Set();

-  constructor(server) {
+  constructor(server: Server) {
    super(server, "/_" + ParentNamespace.count++);
  }

-  _initAdapter() {}
+  /**
+   * @private
+   */
+  _initAdapter(): void {
+    /* no-op */
+  }

-  public emit(...args: any[]): boolean {
-    this.children.forEach(nsp => {
+  public emit(ev: string | Symbol, ...args: [...any]): true {
+    this.children.forEach((nsp) => {
      nsp._rooms = this._rooms;
      nsp._flags = this._flags;
-      nsp.emit.apply(nsp, args);
+      nsp.emit(ev, ...args);
    });
    this._rooms.clear();
    this._flags = {};
@@ -22,16 +28,14 @@ export class ParentNamespace extends Namespace {
    return true;
  }

-  createChild(name) {
+  createChild(name: string): Namespace {
    const namespace = new Namespace(this.server, name);
    namespace._fns = this._fns.slice(0);
-    this.listeners("connect").forEach(listener =>
-      // @ts-ignore
-      namespace.on("connect", listener)
+    this.listeners("connect").forEach((listener) =>
+      namespace.on("connect", listener as (...args: any[]) => void)
    );
-    this.listeners("connection").forEach(listener =>
-      // @ts-ignore
-      namespace.on("connection", listener)
+    this.listeners("connection").forEach((listener) =>
+      namespace.on("connection", listener as (...args: any[]) => void)
    );
    this.children.add(namespace);
    this.server._nsps.set(name, namespace);
--- a/lib/socket.ts
+++ b/lib/socket.ts
@@ -2,24 +2,29 @@ import { EventEmitter } from "events";
 import { PacketType } from "socket.io-parser";
 import url = require("url");
 import debugModule from "debug";
-import { Server } from "./index";
-import { Client } from "./client";
-import { Namespace } from "./namespace";
-import { IncomingMessage } from "http";
-import { Adapter, BroadcastFlags, Room, SocketId } from "socket.io-adapter";
+import type { Server } from "./index";
+import type { Client } from "./client";
+import type { Namespace } from "./namespace";
+import type { IncomingMessage } from "http";
+import type {
+  Adapter,
+  BroadcastFlags,
+  Room,
+  SocketId,
+} from "socket.io-adapter";
 import base64id from "base64id";

 const debug = debugModule("socket.io:socket");

-export const RESERVED_EVENTS = new Set([
+export const RESERVED_EVENTS = new Set(<const>[
  "connect",
  "connect_error",
  "disconnect",
  "disconnecting",
  // EventEmitter reserved events: https://nodejs.org/api/events.html#events_event_newlistener
  "newListener",
-  "removeListener"
-]);
+  "removeListener",
+]) as ReadonlySet<string | Symbol>;

 /**
 * The handshake details
@@ -86,7 +91,7 @@ export class Socket extends EventEmitter {
  > = [];
  private flags: BroadcastFlags = {};
  private _rooms: Set<Room> = new Set();
-  private _anyListeners: Array<(...args: any[]) => void>;
+  private _anyListeners?: Array<(...args: any[]) => void>;

  /**
   * Interface to a `Client` for a given `Namespace`.
@@ -120,16 +125,16 @@ export class Socket extends EventEmitter {
      // @ts-ignore
      secure: !!this.request.connection.encrypted,
      issued: +new Date(),
-      url: this.request.url,
-      query: url.parse(this.request.url, true).query,
-      auth
+      url: this.request.url!,
+      query: url.parse(this.request.url!, true).query,
+      auth,
    };
  }

  /**
   * Emits to this client.
   *
-   * @return {Boolean} Always true
+   * @return Always returns `true`.
   * @public
   */
  public emit(ev: string, ...args: any[]): boolean {
@@ -139,7 +144,7 @@ export class Socket extends EventEmitter {
    args.unshift(ev);
    const packet: any = {
      type: PacketType.EVENT,
-      data: args
+      data: args,
    };

    // access last argument to see if it's an ACK callback
@@ -164,7 +169,7 @@ export class Socket extends EventEmitter {
      this.adapter.broadcast(packet, {
        except: new Set([this.id]),
        rooms: rooms,
-        flags: flags
+        flags: flags,
      });
    } else {
      // dispatch packet
@@ -176,11 +181,11 @@ export class Socket extends EventEmitter {
  /**
   * Targets a room when broadcasting.
   *
-   * @param {String} name
-   * @return {Socket} self
+   * @param name
+   * @return self
   * @public
   */
-  public to(name: Room) {
+  public to(name: Room): Socket {
    this._rooms.add(name);
    return this;
  }
@@ -188,8 +193,8 @@ export class Socket extends EventEmitter {
  /**
   * Targets a room when broadcasting.
   *
-   * @param {String} name
-   * @return {Socket} self
+   * @param name
+   * @return self
   * @public
   */
  public in(name: Room): Socket {
@@ -200,24 +205,22 @@ export class Socket extends EventEmitter {
  /**
   * Sends a `message` event.
   *
-   * @return {Socket} self
+   * @return self
   * @public
   */
-  public send(...args): Socket {
-    args.unshift("message");
-    this.emit.apply(this, args);
+  public send(...args: readonly any[]): Socket {
+    this.emit("message", ...args);
    return this;
  }

  /**
   * Sends a `message` event.
   *
-   * @return {Socket} self
+   * @return self
   * @public
   */
-  public write(...args): Socket {
-    args.unshift("message");
-    this.emit.apply(this, args);
+  public write(...args: readonly any[]): Socket {
+    this.emit("message", ...args);
    return this;
  }

@@ -353,7 +356,7 @@ export class Socket extends EventEmitter {
  private ack(id: number) {
    const self = this;
    let sent = false;
-    return function() {
+    return function () {
      // prevent double callbacks
      if (sent) return;
      const args = Array.prototype.slice.call(arguments);
@@ -362,7 +365,7 @@ export class Socket extends EventEmitter {
      self.packet({
        id: id,
        type: PacketType.ACK,
-        data: args
+        data: args,
      });

      sent = true;
@@ -417,7 +420,7 @@ export class Socket extends EventEmitter {
   *
   * @private
   */
-  _onclose(reason: string) {
+  _onclose(reason: string): Socket | undefined {
    if (!this.connected) return this;
    debug("closing socket - reason %s", reason);
    super.emit("disconnecting", reason);
@@ -427,6 +430,7 @@ export class Socket extends EventEmitter {
    this.connected = false;
    this.disconnected = true;
    super.emit("disconnect", reason);
+    return;
  }

  /**