How to get result from contract function called through web3 using sendTransaction

Question

I use the following to call a solidity contract function in nodejs(v10.14.2) + web3(v0.20.7) + ganache(v1.2.3):

contract.getItemCount(function(err1,result1){
 console.log(result1);
}

result1(datatype BigNumber/uint256) do have the value returned from the contract function.

But sometimes i get out of gas error(ganache gas limit is 90000), I then used the following syntax:

contract.getItemCount.sendTransaction({gas: 200000},function(err1,result1){
 console.log(result1);
}

It executed(consumed 176424 gas) the function successfully. But result1 now has transaction hash as mentioned here. How should i get the result i.e., value returned by the contract function?

Answer 1

If you are calling the callback function of sendTransaction will obviously return the hash. You can also see that in the document you share in question.

You can simply call like this:

contract.getItemCount({gas: 200000}).then(result){
 console.log(result);
}

or

contract.getItemCount({gas: 200000},function(err,res){
   if(!err){
     console.log(res);
   }
})