使用bip39通过助记词生成钱包

/**
 * bip39 and wallet
 */
const bip39 = require('bip39');
const HDKey = require('ethereumjs-wallet/hdkey');

/**
 * 派生子账户
 * @param id
 */
const getChildKey = (id) => {
    const seed = bip39.mnemonicToSeed(mainMne);
    const masterKey = HDKey.fromMasterSeed(seed);
    return masterKey.derivePath("m/44'/60'/0'/0/" + id);
};

/**
 * 获取eth地址
 * @param id
 * @returns {*}
 */
const getAddress = (id) => {
    const childKey = getChildKey(id);
    return childKey.getWallet().getAddressString();

};

/**
 * 获取eth私钥
 * @param id
 * @returns {*}
 */
const getPrivateKey = (id) => {
    const childKey = getChildKey(id);
    return childKey.getWallet().getPrivateKeyString();
};

使用web3.js进行离线签名转账

/**
 * service层
 */
const userService = require('../service/users');

/**
 * web3 and contract
 */
const web3 = require('./web3Util');
const contract = require('../contracts/contract');

//token合约地址
const contractAddress = require('../contracts/address/index');
const EthereumTx = require('ethereumjs-tx');

/**
 * 进行离线签名交易
 * @param uid
 * @param desAddress
 * @param value  eth数量
 * @param tokenValue  token数量
 * @returns {Promise<void>}
 */
const sendEthTransaction = async (uid, desAddress, value, tokenValue) => {

    //获取数据库对象
    const findUser = await userService.findById(uid);

    //获取私钥
    const privateKeyString = decodePrivateKey(findUser.ethPrivateKey).substring(2);
    const privateKey = Buffer.from(privateKeyString, 'hex');

    //iValue 转账金额
    let dataAbi = "";
    let iValue;
    let toAddress;
    let gasLimit;
    if(tokenValue !== 0 && tokenValue !=="0") {
        //获取转账数据abi
        dataAbi = contract.methods.transfer(desAddress, tokenValue.toString()).encodeABI();
        logger.debug("data:" + dataAbi);
        iValue = 0;
        toAddress = contractAddress;
        gasLimit = await contract.methods.transfer(desAddress, tokenValue.toString()).estimateGas({from: findUser.ethAddress});

    } else {
        iValue = parseInt(value);
        toAddress = desAddress;
        gasLimit = 21000;
    }

    //gas
    const gasPrice = await web3.eth.getGasPrice();

    logger.debug("gasLimit: " + gasLimit);

    //nonce
    let nonce = await web3.eth.getTransactionCount(findUser.ethAddress, "pending");
    logger.debug("nonce: " + nonce);

    const txParams = {
        nonce: toHex(nonce),
        gasPrice: toHex(gasPrice * gasPriceFactor),
        gasLimit: toHex(gasLimit),
        to: toAddress,
        value: toHex(iValue),
        data: dataAbi,
        chainId: chainId
    };

    const tx = new EthereumTx(txParams);
    tx.sign(privateKey);
    const serializedTx = tx.serialize();

    const block = await web3.eth.sendSignedTransaction(toHex(serializedTx));
    logger.debug(block.transactionHash);

    return block;
};

tips： sendEthTransaction方法将eth转账和token转账合并，转账eth时将tokenValue赋值为0，转账token时将value赋值为0即可