How to get transaction hash of a function call from web3?

Question

Lets say I use web3 to call foo.bar() like so:

var foo = await Foo.deployed();
var result = await foo.bar();

If I console.log(result) I just see something that says [Object object]

How can I get the transaction hash of the function call? I'd like to be able to keep track of its status. e.g. failed, pending etc.

Thanks!

Answer 1

This depends if you are using the new beta version of web3.js 1.0 or the older 0.x version:

from the web3 1.0 beta documentation:

myContract.methods.myMethod(123).send({from: '0xde0B295669a9FD93d5F28D9Ec85E40f4cb697BAe'})
    .on('transactionHash', function(hash){
        console.log(hash);
})

in web3 0.x you can see here how to call a smart contract function and then look here for the return value:

var txHash = myContractInstance.myMethod(param1, param2);
console.log(txHash);

Answer 2

If you have a signedTransaction object, you can run

var transactionHash = web3.utils.sha3(signedTx, { encoding: "hex" });

https://web3js.readthedocs.io/en/1.0/web3-utils.html?highlight=utils#sha3 https://web3js.readthedocs.io/en/1.0/web3-eth-accounts.html#signtransaction