How to use async to get event logs in the for loop?

Question

I want to get event log to do other thing, so I try to use for loop to get the event log in the websjs.

I try to use async and await, but order is wrong.

Here is my web3js sample code

    handleContractHistory: async function(event){
        var log_info = {};
        var abi = App.contracts.Crowdsale.abi;
        var ClientReceipt = web3.eth.contract(abi);
        var clientReceipt = ClientReceipt.at(my_contract_address);
        var event = clientReceipt.PurchaseLogs({}, {fromBlock: 0, toBlock: 'latest'});

        await event.get(function(error, logs){

          for(var index = 0; index < logs.length; index ++){
            log_info[logs[index].blockHash] = 1;
            console.log(logs[index].blockHash);
          }

        });

        console.log(log_info);
    }

Here is the result of console

{}
0x6b6c29cd8c693205d41*****************
0x6b628cd04b093b731e1*****************
0x6b6c29cd8c645eb54f2*****************

Does that have other way that can let function to wait to get the data in the loop?

Answer 1

You can create a promise function and use await for waiting until all events are collected, just like below code.

Promise function:

const WaitAllContractEventGet = function(myevent) {
    return new Promise(function(resolve, reject) {
        myevent.get(function(error, logs) {
            if (error !== null) {
                reject(error);
            }
            var log_info = {};
            for (var index = 0; index < logs.length; index++) {
                log_info[logs[index].blockHash] = 1;
                console.log(logs[index].blockHash);
            }                                                                                                                   
            resolve(log_info);
        });
    });
};

Callee:

handleContractHistory: async function(event){
    var log_info = {};
    var abi = App.contracts.Crowdsale.abi;
    var ClientReceipt = web3.eth.contract(abi);
    var clientReceipt = ClientReceipt.at(my_contract_address);
    var event = clientReceipt.PurchaseLogs({}, {fromBlock: 0, toBlock: 'latest'});
    const log_info = await WaitAllContractEventGet(event);
    console.log(log_info);
}