Web3.js and Events – Is There a Way to Get All of a Contract’s Events as an Array

eventsweb3js

I'm using Web3's allEvents() method to get all the events on a specific contract, and it's working great, except each event pops into the callback separately.

That turns into a bit of a pain when I want to create an array of all the events, as it's hard to discern when the callback has been fired 'enough' times.

Is there a method – in Web3 or otherwise – to get all the events as one array?

Best Answer

I figured it out almost immediately. Instead of using

myContract.allEvents(filterObject, (e, res) => console.log(res))

I should have been using

myContract.allEvents(filterObject).get((e, res) => console.log(res))

Related Solutions

Web3.js – Parsing Transaction Receipt Logs

Do this: You'll need to pull code from web3, and it works best if your frontend is bundled using something like webpack or browserify:

var SolidityCoder = require("web3/lib/solidity/coder.js");
var log = receipt.logs[0];
var data = SolidityCoder.decodeParams(["string", "uint"], log.data.replace("0x", ""));

In this case, we're decoding log data that contains two variables, one a string type and one a uint.

EDIT:

If you have the ABI available, you can detect which event it is related to that ABI:

var SolidityCoder = require("web3/lib/solidity/coder.js");

// You might want to put the following in a loop to handle all logs in this receipt.
var log = receipt.logs[0];
var event = null;

for (var i = 0; i < abi.length; i++) {
  var item = abi[i];
  if (item.type != "event") continue;
  var signature = item.name + "(" + item.inputs.map(function(input) {return input.type;}).join(",") + ")";
  var hash = web3.sha3(signature);
  if (hash == log.topics[0]) {
    event = item;
    break;
  }
}

if (event != null) {
  var inputs = event.inputs.map(function(input) {return input.type;});
  var data = SolidityCoder.decodeParams(inputs, log.data.replace("0x", ""));
  // Do something with the data. Depends on the log and what you're using the data for.
}

Web3.js – How to Get Past Events and Watch Future Events Separately

Semantically, past events are a finite list, while future events are an infinite list (i.e. stream). The latter can encompass the former, but not the other way around, i.e. you could represent all past and future events as a stream. This is not built in, but it wouldn’t be hard to implement if you really wanted to:

function allEvents(ev, cb) {   
  ev({}, { fromBlock: 0, toBlock: 'latest' }).get((error, results) => {
    if(error) return cb(error)
    results.forEach(result => cb(null, result))
    ev().watch(cb)   
  }) 
}

...

allEvents(myContract.myEvent, (error, e) => {
  ...
})

Best Answer

Related Solutions

Web3.js – Parsing Transaction Receipt Logs

Web3.js – How to Get Past Events and Watch Future Events Separately

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