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通过私有以太坊区块链在浏览器中实时更新用户余额

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Problem

我想有一个网站，通过私人以太坊区块链更新用户的财富 .

Current Solution (broken)

我打开一个websocket到一个私有的以太坊区块链，我想在前端更新我的coinbase余额 . 我的代码如下：

const express    = require("express");
const Web3       = require("web3");


var app  = express();

app.get("/", (req, res) => res.send("hello world from ping ether application"));
app.get("/ping-ether", function(req, res){


    var web3 = new Web3(new Web3.providers.WebsocketProvider('ws://localhost:8546'));

    var event_newBlockHeaders = web3.eth.subscribe("newBlockHeaders", function(err, result){

        if (err){ 

            console.log(err) 

        } else {

            let acctPromise = web3.eth.getAccounts().then(function(accts){

                let balance = web3.eth.getBalance(accts[0]).then(function(bal){

                    console.log("user: ", accts[0]);
                    console.log("balance: ", bal);

                    res.end("new balance for user: " + bal)

                });

            });
        }

    });


});


// run the server
app.listen(3000, () => console.log("web app listening on port 3000"));

很明显，这并不是在前端更新，即使最内部的回调是持续不断的，因为我可以在控制台上确认 . 我想要三件事：

  • 如何更改此代码，以便前端具有coinbase余额的实时代码

  • 一般来说代码的嵌套承诺闻起来很糟糕 . 我如何重构它以便每次导航到 /ping-ether 时都不必 Build websocket连接？

  • 欢迎任何其他建议 . 我很新 node.js

javascript node.js express ethereum web3

2 回答

  • 1

    未经测试，但这样的事情应该有效：

    const express    = require("express");
const Web3       = require("web3");

var app  = express();
var web3 = new Web3(new Web3.providers.WebsocketProvider('ws://localhost:8546'));
var balance = -1;

web3.eth.getAccounts().then(accounts => {
  return web3.eth.subscribe("newBlockHeaders", (err, result) => {
    if (err) {
      console.log(err);
    } else {
      web3.eth.getBalance(accounts[0]).then(bal => {
        console.log("user: ", accounts[0]);
        console.log("balance: ", bal);
        balance = bal;
      });
    }
  })
}).then(() => {
  app.listen(3000, () => console.log("web app listening on port 3000"));
});

app.get("/", (req, res) => res.send("hello world from ping ether application"));
app.get("/ping-ether", function (req, res) {
  res.end("new balance for user: " + balance);
});

    主要思想是设置websocket连接和订阅一次，然后只使用当前余额响应传入的Web请求 . 我还尝试通过返回订阅承诺来清理嵌套的promises .

    回复于
  • 2

    更新：我最终使用websocket，这是解决方案：

    import * as Web3     from 'web3'     ; 
import * as express  from 'express'  ;
import * as socketIO from 'socket.io';
import * as http      from 'http'    ;


const CLIENT_PATH = 'path/to/directory'

var app    = express();
var server = http.Server(app);
var io     = socketIO(server);
var web3   = new Web3(new Web3.providers.WebsocketProvider('ws://localhost:8546'));

app.get('/', (req,res) => {
    res.sendFile(CLIENT_PATH + '/index.html');
});


web3.eth.getAccounts().then(accounts => {

    display_account(accounts)
})

function display_account(accounts){

    var user_0 = accounts[0]

    web3.eth.subscribe('newBlockHeaders', (err, ret) => {

        if (err){ 

            console.log("error: ", err)

        } else {

            web3.eth.getBalance(user_0).then(bal => {

                var msg = 'Balance for user ' + user_0 + ' is ' + bal  
                io.emit('message-1', msg)
                console.log('emitted message: ', msg)

            })
        }

    })

}


// use this instead of app.listen
server.listen(3000, () => {

    console.log('listening on 3000')

});

    这是index.html .

    <html>
<head></head>

<body>
  <div id="message"></div>

  <script src="/socket.io/socket.io.js"></script>
  <script>

    var socket = io();

    socket.on('message-1', function(msg){
      console.log(msg);
      document.getElementById("message").innerHTML = msg;
    });

  </script>
</body>
</html>
    回复于

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