Watch multiple contracts/events?

Question

Is there a way to watch events from multiple contracts with just one watch-statement (something like [contract1.event, contract2.event, ...].watchAll() ) in Javascript?

Code is just for illustration purposes:

   var event = contract.EventName({from: address}); // watching multiple contracts/events possible?
   event.watch(function(err, result) {
         ...
   });

Answer 1

There is a build in function to listen all the events in one watch statement

var events = myContractInstance.allEvents([additionalFilterObject]);

// watch for changes
events.watch(function(error, result){
  if (!error)
    console.log(result);
});

additionalFilterObject can used to filter the results; example adding an address would be {address: myAddress}

On the other hand doesn't seems possible to filter the events using the names unless you specify the topics on the additionalFilterObject where the topic addresses are the event/function hash (keccak256 of your event name eg. keccak256('EventName1(uint)')) then you would have something like:

var events = myContractInstance.allEvents({address: myAddress, topics: [['0x1234...', '0x5678...']]});

// watch for changes
events.watch(function(error, result){
  if (!error)
    console.log(result);
});

but you can check the event result and filter the event name according to the events you want to listen:

var events = myContractInstance.allEvents([additionalFilterObject]);

// watch for changes
events.watch(function(error, result){
  if (!error) {
    if(['EventName1', 'EventName2'].includes(result.event)) {
       //do
    }
  }
});

and that would be more readable maybe. Another less elegant solution could be

var event1 = contract.EventName1({from: address});
var event2 = contract.EventName2({from: address});
event1.watch(myCallback);
event2.watch(myCallback);

function myCallback(err, result) {
}

Answer 2

method allEvents() will not work for "web3": "^1.0.0-beta.36". This will throw an error

allEvents is not a function

This will not work even for some other versions. Refer here https://github.com/ethereum/web3.js/issues/989 It didnt work for me as well, I am using "web3": "^1.0.0-beta.36". If someone has an alternative, do share.