Moved to ts (#6593)

* Moved to ts

* Fixed type check

* Removed js suffixes

* Migrated to ts

* Fixed ts.

* Fixed type check

* Installed missing d ts

src/static/js/socketio.ts

@@ -0,0 +1,49 @@
+// @ts-nocheck
+import io from 'socket.io-client';
+
+/**
+ * Creates a socket.io connection.
+ * @param etherpadBaseUrl - Etherpad URL. If relative, it is assumed to be relative to
+ *     window.location.
+ * @param namespace - socket.io namespace.
+ * @param options - socket.io client options. See
+ *     https://socket.io/docs/v2/client-api/#new-Manager-url-options
+ * @return socket.io Socket object
+ */
+const connect = (etherpadBaseUrl, namespace = '/', options = {}) => {
+  // The API for socket.io's io() function is awkward. The documentation says that the first
+  // argument is a URL, but it is not the URL of the socket.io endpoint. The URL's path part is used
+  // as the name of the socket.io namespace to join, and the rest of the URL (including query
+  // parameters, if present) is combined with the `path` option (which defaults to '/socket.io', but
+  // is overridden here to allow users to host Etherpad at something like '/etherpad') to get the
+  // URL of the socket.io endpoint.
+  const baseUrl = new URL(etherpadBaseUrl, window.location);
+  const socketioUrl = new URL('socket.io', baseUrl);
+  const namespaceUrl = new URL(namespace, new URL('/', baseUrl));
+
+  let socketOptions = {
+    path: socketioUrl.pathname,
+    upgrade: true,
+    transports: ['websocket'],
+  };
+  socketOptions = Object.assign(options, socketOptions);
+
+  const socket = io(namespaceUrl.href, socketOptions);
+
+  socket.on('connect_error', (error) => {
+    console.log('Error connecting to pad', error);
+    /*if (socket.io.engine.transports.indexOf('polling') === -1) {
+      console.warn('WebSocket connection failed. Falling back to long-polling.');
+      socket.io.opts.transports = ['websocket','polling'];
+      socket.io.engine.upgrade = false;
+    }*/
+  });
+
+  return socket;
+};
+
+if (typeof exports === 'object') {
+  exports.connect = connect;
+} else {
+  window.socketio = {connect};
+}