// 构造出合约调用交易

var contract = new web3.eth.Contract(contractJson, contractAddress);
var transfer = contract.methods.transfer("0x...", 490);
var encodedABI = transfer.encodeABI();
var tx = {
    from: "0x...",
    to: contractAddress,
    gas: 2000000,
    data: encodedABI
  }; 

 // 对交易签名
web3.eth.accounts.signTransaction(tx, privateKey).then(signed => {
    var tran = web3.eth.sendSignedTransaction(signed.rawTransaction);
    tran.on('confirmation', (confirmationNumber, receipt) => {
      console.log('confirmation: ' + confirmationNumber);
    });
    tran.on('transactionHash', hash => {
      console.log('hash');
      console.log(hash);
    });
    tran.on('receipt', receipt => {
      console.log('reciept');
      console.log(receipt);
    });
    tran.on('error', console.error);
  });