How to access the event log by knowing the contract address (web3)?

Question

How can I access a log stored in one of the tx of the contract via web3?

Code example:

event newtest(string indexed name, uint indexed idlevel,string indexed multib, string objmulti, uint objnm);

and

newtest('test',5,'testj','obj2',30);

Let's say contract address is 0x00. How do I get all the logs that are stored in this contract address with web3?

P.s. I don't need to listen on events in real time. I just need to get all the logs of a contract, based on filters when I need it.

Answer 1

Take a look at web3.eth.filter and watch.

Something like this:

const filter = web3.eth.filter({
  fromBlock: 0,
  toBlock: 'latest',
  address: contractAddress,
  topics: [web3.sha3('newtest(string,uint256,string,string,uint256)')]
})

filter.watch((error, result) => {
   //
})

Note the part that "In Solidity: The first topic is the hash of the signature of the event." Canonical types, such as uint256 have to be used in signatures.

EDIT: Per @plingamp's comment web3.sha3 now includes the '0x'.

Answer 2

Use .get instead of .watch with web3.eth.filter:

contractAddress = "0x00.."
web3.eth.filter({
  address: contractAddress,
  from: 1,
  to: 'latest'
}).get(function (err, result) {
  // callback code here
})

Answer 3

In web3 1.0 you can use getPastEvents as follows

 var contractInstance = new web3.eth.Contract(contractAbi, contractAddress);

  contractInstance.getPastEvents('EventName', {
      filter: {id: id},  
      fromBlock: 0,
      toBlock: 'latest'
  }, (error, events) => { 

      if (!error){
        var obj=JSON.parse(JSON.stringify(events));
        var array = Object.keys(obj)

        console.log("returned values",obj[array[0]].returnValues);

      }
      else {
        console.log(error)
      }})

Answer 4

Yes, one way to go is write all of your conditions in a .js file and load these script to console when you need.

loadScript -> Loads a JavaScript file and executes it.

loadScript example

Answer 5

If you what to filter for multiple events you must pass in a list within a list. For the following two events emitted in a Solidity contract:

event event1(uint256 indexed anumb)
event event2(uint256 indexed anothernumb)
event event3(uint256 indexed yetanothernumb)

Use the following to filter for events1 and event2 only:

const filter = web3.eth.filter({
  fromBlock: 0,
  toBlock: 'latest',
  address: contractAddress,
  topics: [[web3.sha3('event1(uint256)'),web3.sha3('event2(uint256)')]]
})

filter.get((error, result) => {
   // gets all prior results
})

From the docs:

topics: Array of Strings - An array of values which must each appear in the log entries. The order is important, if you want to leave topics out use null, e.g. [null, '0x00...']. You can also pass another array for each topic with options for that topic e.g. [null, ['option1', 'option2']]