I have some JavaScript that's connecting to a private ethereum network via JSON-RPC. I am trying to extract the transaction hash of the blocks but am unable to do so.

// BlockNumber
        function(err, res) {
          if (err) console.log(err)
          console.log("MINER ONE block number: " + parseInt(res.result, 16) )
          miner_one_block_number = parseInt(res.result, 16);

        // console.log("BLOCK NUMBER: " + miner_one_block_number);

// Block Hash
clientNodeOne.call({"jsonrpc":"2.0","method":"eth_getBlockByNumber","params":[miner_one_block_number, false],"id":1},
      function(err, res) {
        if (err) console.log(err)
        console.log("MINER ONE transaction hash: " + res.result)

The first call to read the block number works great. I am saving the block number to another variable, miner_one_block_number. I am then passing that variable into the input parameters for the call to eth_getBlockByNumber. Instead of getting the transaction hash for that block, I am instead getting a value of undefined. Any help would be appreciated!


This is failing because the block number passed as the first parameter to eth_gasBlockByNumber must be a hex string. Instead of doing parseInt(res.result, 16), just store res.result directly and pass that in.

  • Hey I removed the parse int and stored the res.result directly. But instead of undefined, I get an [object Object]. Any ideas? Thank you for your help btw. – Sameet Ahmed Nov 13 '19 at 17:06
  • Nevermind got it! Used stringify to get the result. – Sameet Ahmed Nov 13 '19 at 17:27

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