How can you work around Web3 1.0s bug to check for transaction confirmation?

Question

The following includes a null Tx id:

web3.eth.getTransaction('0x2fc36f9c6593bc1232b3466832c6ee38b5b2b3b4a54be3f6c68fb06e8d82e452', function(error, result){ 
  if (!error) {
    console.log(result.blockNumber)
  }
})

You would expect this to log null or undefined, but it throws in Web3.js 1.2.1. This makes it impossible to use getTransaction with polling to see if a transaction is confirmed.

checkTx()
function checkTx() {
    web3.eth.getTransaction('0x2fc36f9c6593bc1232b3466832c6ee38b5b2b3b4a54be3f6c68fb06e8d82e452')
        .then((result) => {
            if (result.blockNumber != null) {
                console.log(result.value)
            } else {
                console.log('Not confirmed.')
                setTimeout(() => { checkTx() }, 1000)
            }
        })
} 

In both case you get this error when the Tx blockNumber is null: TypeError: Cannot read property 'blockNumber' of null

How can I check that a transaction id is confirmed by polling if I can't evaluate the property of the blockNumber?

Answer 1

In your first example, you are trying to print result.blockNumber without verifying first that the result object is valid.

In your second example, you are referring to the first input parameter of the callback function as if it was the result object, when it is in fact the error object.

In short, try this:

web3.eth.getTransaction('0x2fc3...', function(error, result) { 
    if (result && result.blockNumber) {
        console.log(result.value);
    }
    else {
        console.log('Not confirmed');
        setTimeout(() => {checkTx()}, 1000);
    }
});