Request user to sign state changing transaction with metamask using Infura and web3js

Question

Can't seem to find the right function to ask the user to sign a transaction via metamask, this is my code so far:

  const bet = '102500000000000010'
  const account = '0xc8133b744147078a551b8d9c547414d427d8f579'

  web3.eth.getTransactionCount(account, function (err, nonce) {
    const data = Contract.methods.payBet(1553399554260556, bet).encodeABI();
    const tx = new Tx({
      nonce,
      gasPrice: 165335,
      gasLimit: 100000,
      to: "0x232b....",
      value: bet,
      data,
    })

    //THIS tx.sign SHOULD BE THE METAMASK PART, since I dont have the user PK
    tx.sign(ethereumjs.Buffer.Buffer.from(privateKey, 'hex'));

    var raw = '0x' + tx.serialize().toString('hex');
    web3.eth.sendSignedTransaction(raw, function (err, transactionHash) {
      console.log(transactionHash);
    });
  });

What should I do to ask the user to sign the tx? I also tried to use web3.eth.sendTransaction but it is not supported by infura.

I'm abit lost here

Answer 1

Just use web3.eth.sendTransaction instead of web3.eth.sendSignedTransaction and Metamask will ask user to sign your transaction, and then will send signed transaction to Infura. See Metamask FAQ for more details.