Javascript RPC CORS bridge

Simple javascript library that implements RPC with star topology for cross-origin interaction between single host and some independent client widgets. It allows straight usage of widgets loaded to iframes from the different domains avoiding CORS limitations.

Host can broadcast simple events of different types to all clients and handle specified client's requests.

Clients can receive specified events from host and make requests of different types. Host can reply to client's request with continuous progress, successful response or error statement.

Running host

To run a host load module bridgehost.js and subscribe handlers to the desired request types:

// subscribe to the 'auth' requests from any client
BridgeHost.onrequest('auth', function(request, login, password) {
  // try to authorize
  if (login !== 'user' || password !== 'P@$$') {
      // reply with error statement as first argument
      request.response({ code: 1, message:'No such login or password' });
      return;
  }
  
  // send some optional authorization progress 
  request.progress(0.25); // a quarter is done
  request.progress(0.50);// a half is done

  // reply with successful response with empty error and rest arguments
  request.response(null, 'Nickname', { canSpeak: true, canKick: true });
})

// broadcast update event 'messages' between all clients, so every
// subscriber can ignore it or request changes made since last update
BridgeHost.dispatch('messages', { room: 'chat', ts: 1564861965202 });

Running clients

To run a client load module bridgeclient.js, create instance of client bridge endpoint and subscribe handlers to the desired event types:

// create client bridge
var bridge = new BridgeClient();

// subscribe to the 'messages' event
bridge.onevent('messages', function(data) {
  // check for context and time of update at event payload
  if (data.room !== currentRoom || data.ts <= lastUpdateTime) return;
  
  // request new data if it has been changed
  var handler = bridge.request('list', currentRoom);
  handler.onprogress = function(state) {
    // handle progress of request processing
    console.log(state);
  }
  handler.onresponse = function(error, messages) {
    if (error) {
      // handle error statement of request
      console.error(error);
    } else {
      // update messages within current room
      currentMessages = messages;
      lastUpdateTime = Date.now();
    }
  }
})