Implementation of blockchain with JS

1. Go is an open source programming language, which makes it easy to construct simple, reliable and efficient software. If you want to learn this programming language, you should first find a good tutorial. Brother Lian's go language + blockchain training has recently published a new set of go language tutorial, and the teacher's speaking is very good

with the global hot discussion of the concept of "blockchain", the application of blockchain technology has been quietly added to the daily life scenes such as finance, logistics, credit reference, manufacturing and retail. Some experts have shown that the future blockchain will be closely related to people's lives, and the integration of blockchain technology and people's daily life is the general trend

the popularity of the blockchain market has triggered a large number of talents demand based on blockchain technical personnel, and the popularity of blockchain talents is rising at the speed of light. According to the "2018 blockchain high salary list" released by lagou.com, Tencent, Xiaomi, Suning, Jingdong and other domestic enterprise giants have released many high salary blockchain post demands, trying to explore blockchain related technologies and applications. It is also pointed out in the list that the demand for high salary jobs is mainly based on blockchain related technical jobs, among which Suning and Keda have been given the highest monthly salary of 100k

the huge market demand for technical talents will inevitably lead to the explosive emergence and growth of the whole blockchain training market. Most of the training modes can be divided into online training, traditional IT organization training, and offline short-term training camps, which mainly focus on high-end forms. However, in the process of the hot market evolution, there are also a variety of blockchain training chaos: lecturers' qualifications are watered down, and even the most basic names are not disclosed, the syllabus is opaque, and the teaching quality is shrinking, Unreasonable class arrangement and uneven training fees and so on

with the large-scale development of the whole blockchain training market, brother company ecation, together with Yin Cheng, a senior blockchain expert, and his Tsinghua Shuimu Weiming team, has set up a blockchain college. With its professional and powerful team of technical lecturers, detailed and comprehensive curriculum system, and a large number of authentic enterprise blockchain projects, it aims to deepen the blockchain teaching and training field, And train more professional technical talents for enterprises and society<

Yin Cheng, a senior blockchain technology expert, graated from Tsinghua University, is the dean of brother Lian blockchain college. He once served as Google Algorithm Engineer, the world's most valuable expert in the field of Microsoft blockchain, and the gold medal lecturer of Microsoft tech.ed conference. Proficient in C / C + +, python, go language, sicikit learn and tensorflow. With 15 years of programming experience and 5 years of teaching experience, senior software architect, Intel Software Technology expert, famous technology expert, with many years of working experience in the world's top it company Microsoft Google. He has many years of experience in software programming and lecturing, and has developed many procts in human-computer interaction, ecation, information security, advertising and blockchain system. He has deep experience in project management and R & D, has two AI invention patents, and has practical experience in developing e-money deployed to Microsoft Windows azure. Teaching explanation is in simple language, so that students can apply what they have learned
the first stage: blockchain instry and go programming for 5 weeks
the second stage: cryptography and consensus algorithm for 2 weeks
the third stage: Ethereum source code analysis and development for 3 weeks
the fourth stage: Super ledger and node.js for 2 weeks
the fifth stage: bitcoin & EOS for 4 weeks
the sixth stage: comprehensive actual combat of the project

2. If it's me, I'll choose ash and only do the application layer. Of course, the easier I get to know, the better

3. 1. Web Design: HTML5, CSS, JS
2. Web back end required: PHP
3. JavaWeb is also very important, but if your Java foundation is not good, and you have not learned JavaWeb technology, then it is recommended that you do not use this technology
3. Mobile development technology, such as Android development, compared with the web class, it is also good to use variant small programs, However, you haven't learned and don't recommend to start
4. For mobile terminals, cross platform requirements should be better, so it is recommended that you learn ionic + Cordova + angular framework to develop cross platform mobile applications
of course, the first step is, do you want to be a mobile terminal, a PC terminal or a platform terminal?

4. Do you want to learn blockchain development technology or just want to know what blockchain is? If it is the former, you can look at the code of other blockchain projects and learn about it first. If it is the latter, we can pay attention to some good blockchain we media. Blockchain is an emerging instry. There is no ready-made training course. It depends on self exploration and understanding.

5. What a tigress Cried Mrs Linton, letting her go, shaking her hand in pain“ For God's sake,

6. This needs to be created with the help of the platform
the hypervessel platform developed by IBM China Research Institute provides a blockchain development and testing environment for blockchain enthusiasts and developers. Through this platform, users can create a multi node blockchain based on hyperledger fabric free of charge and quickly, and play smart contracts on their own chains
of course, decent, a foreign decentralized content sharing platform, can also be created.

7. The Internet has just begun, intelligent life coming

8. <span style="font-family:Arial, Helvetica, sans-serif;">'use strict';</span>var CryptoJS = require("crypto-js");var express = require("express");var bodyParser = require('body-parser');var WebSocket = require("ws");var http_port = process.env.HTTP_PORT || 3001;var p2p_port = process.env.P2P_PORT || 6001;var initialPeers = process.env.PEERS ? process.env.PEERS.split(',') : [];class Block { constructor(index, previousHash, timestamp, data, hash) { this.index = index; this.previousHash = previousHash.toString(); this.timestamp = timestamp; this.data = data; this.hash = hash.toString(); }}var sockets = [];var MessageType = { QUERY_LATEST: 0, QUERY_ALL: 1, RESPONSE_BLOCKCHAIN: 2};var getGenesisBlock = () => { return new Block(0, "0", 1465154705, "my genesis block!!", "");};var blockchain = [getGenesisBlock()];var initHttpServer = () => { var app = express(); app.use(bodyParser.json()); app.get('/blocks', (req, res) => res.send(JSON.stringify(blockchain))); app.post('/mineBlock', (req, res) => { var newBlock = generateNextBlock(req.body.data); addBlock(newBlock); broadcast(responseLatestMsg()); console.log('block added: ' + JSON.stringify(newBlock)); res.send(); }); app.get('/peers', (req, res) => { res.send(sockets.map(s => s._socket.remoteAddress + ':' + s._socket.remotePort)); }); app.post('/addPeer', (req, res) => { connectToPeers([req.body.peer]); res.send(); }); app.listen(http_port, () => console.log('Listening http on port: ' + http_port));};var initP2PServer = () => { var server = new WebSocket.Server({port: p2p_port}); server.on('connection', ws => initConnection(ws)); console.log('listening websocket p2p port on: ' + p2p_port);};var initConnection = (ws) => { sockets.push(ws); initMessageHandler(ws); initErrorHandler(ws); write(ws, queryChainLengthMsg());};var initMessageHandler = (ws) => { ws.on('message', (data) => { var message = JSON.parse(data); console.log('Received message' + JSON.stringify(message)); switch (message.type) { case MessageType.QUERY_LATEST: write(ws, responseLatestMsg()); break; case MessageType.QUERY_ALL: write(ws, responseChainMsg()); break; case MessageType.RESPONSE_BLOCKCHAIN: handleBlockchainResponse(message); break; } });};var initErrorHandler = (ws) => { var closeConnection = (ws) => { console.log('connection failed to peer: ' + ws.url); sockets.splice(sockets.indexOf(ws), 1); }; ws.on('close', () => closeConnection(ws)); ws.on('error', () => closeConnection(ws));};var generateNextBlock = (blockData) => { var previousBlock = getLatestBlock(); var nextIndex = previousBlock.index + 1; var nextTimestamp = new Date().getTime() / 1000; var nextHash = calculateHash(nextIndex, previousBlock.hash, nextTimestamp, blockData); return new Block(nextIndex, previousBlock.hash, nextTimestamp, blockData, nextHash);};var calculateHashForBlock = (block) => { return calculateHash(block.index, block.previousHash, block.timestamp, block.data);};var calculateHash = (index, previousHash, timestamp, data) => { return CryptoJS.SHA256(index + previousHash + timestamp + data).toString();};var addBlock = (newBlock) => { if (isValidNewBlock(newBlock, getLatestBlock())) { blockchain.push(newBlock); }};var isValidNewBlock = (newBlock, previousBlock) => { if (previousBlock.index + 1 !== newBlock.index) { console.log('invalid index'); return false; } else if (previousBlock.hash !== newBlock.previousHash) { console.log('invalid previoushash'); return false; } else if (calculateHashForBlock(newBlock) !== newBlock.hash) { console.log(typeof (newBlock.hash) + ' ' + typeof calculateHashForBlock(newBlock)); console.log('invalid hash: ' + calculateHashForBlock(newBlock) + ' ' + newBlock.hash); return false; } return true;};var connectToPeers = (newPeers) => { newPeers.forEach((peer) => { var ws = new WebSocket(peer); ws.on('open', () => initConnection(ws)); ws.on('error', () => { console.log('connection failed') }); });};var handleBlockchainResponse = (message) => { var receivedBlocks = JSON.parse(message.data).sort((b1, b2) => (b1.index - b2.index)); var latestBlockReceived = receivedBlocks[receivedBlocks.length - 1]; var latestBlockHeld = getLatestBlock(); if (latestBlockReceived.index > latestBlockHeld.index) { console.log('blockchain possibly behind. We got: ' + latestBlockHeld.index + ' Peer got: ' + latestBlockReceived.index); if (latestBlockHeld.hash === latestBlockReceived.previousHash) { console.log("We can append the received block to our chain"); blockchain.push(latestBlockReceived); broadcast(responseLatestMsg()); } else if (receivedBlocks.length === 1) { console.log("We have to query the chain from our peer"); broadcast(queryAllMsg()); } else { console.log("Received blockchain is longer than current blockchain"); replaceChain(receivedBlocks); } } else { console.log('received blockchain is not longer than received blockchain. Do nothing'); }};var replaceChain = (newBlocks) => { if (isValidChain(newBlocks) && newBlocks.length > blockchain.length) { console.log('Received blockchain is valid. Replacing current blockchain with received blockchain'); blockchain = newBlocks; broadcast(responseLatestMsg()); } else { console.log('Received blockchain invalid'); }};var isValidChain = (blockchainToValidate) => { if (JSON.stringify(blockchainToValidate[0]) !== JSON.stringify(getGenesisBlock())) { return false; } var tempBlocks = [blockchainToValidate[0]]; for (var i = 1; i < blockchainToValidate.length; i++) { if (isValidNewBlock(blockchainToValidate[i], tempBlocks[i - 1])) { tempBlocks.push(blockchainToValidate[i]); } else { return false; } } return true;};var getLatestBlock = () => blockchain[blockchain.length - 1];var queryChainLengthMsg = () => ({'type': MessageType.QUERY_LATEST});var queryAllMsg = () => ({'type': MessageType.QUERY_ALL});var responseChainMsg = () =>({ 'type': MessageType.RESPONSE_BLOCKCHAIN, 'data': JSON.stringify(blockchain)});var responseLatestMsg = () => ({ 'type': MessageType.RESPONSE_BLOCKCHAIN, 'data': JSON.stringify([getLatestBlock()])});var write = (ws, message) => ws.send(JSON.stringify(message));var broadcast = (message) => sockets.forEach(socket => write(socket, message));connectToPeers(initialPeers);initHttpServer();initP2PServer();

9. This book tries to use less space to explain the related content of node.js blockchain development to readers. There are five parts in this book: * part describes the related concepts of blockchain proct cryptocurrency in detail; The second part introces the introction of node.js in detail, and completes the investigation and description of node.js in the field of blockchain technology through a specific project; The third part analyzes the design principle of blockchain layer by layer from the perspective of architecture design, and deeply interprets the related concepts and technologies; The fourth part is still based on the actual projects involved in the Yishu project, including a number of complete and independent small projects; The fifth part is the appendix, which gives the bilingual list of blockchain related terms in Chinese and English, the explanation of related professional terms and the relevant information of blockchain club.