使用javascript实现简单的区块链（签名+工作量证明机制）(代码片段)

//区块链 block chain
//data 之前区块的哈希值 当前区块的哈希值：是由存储在区块里的信息算出来的（data + 之前区块的哈希值）

const sha256 = require('./crypto-js/sha256')

//区块
class Block
    constructor(data)
        this.data = data
        this.previousHash = ''
        this.nonce = 1
        this.hash = this.computeHash()
    

    computeHash()
        return sha256(this.data + this.previousHash + this.nonce).toString()
    

    // 计算符合区块链难度的hash值
    mine(difficulty)
        while(true)
            this.hash = this.computeHash()
            if(this.hash.substring(0, difficulty) !== this.getAnswer(difficulty))
                this.nonce++
            else
                break
            
        
    

    getAnswer(difficulty)
        // 开头前n位为0的hash
        let answer = ''
        while(difficulty-- !== 0)
            answer += '0'
        
        return answer
    


//区块 的 链 
//生成祖先区块
class Chain
    constructor()
        this.chain = [this.bigBang()]
        this.difficulty = 4
    

    bigBang()
        const genesisBlock = new Block('祖先区块')
        return genesisBlock
    

    //获取最新一个区块
    getLatestBlock()
        return this.chain[this.chain.length-1]
    

    //添加新区块
    addBlockToChain(newBlock)
        // 1、data 2、previousHash
        newBlock.previousHash = this.getLatestBlock().hash
        newBlock.hash = newBlock.computeHash()
        // 进行挖矿
        newBlock.mine(this.difficulty)
        this.chain.push(newBlock)
    

    //区块链验证 当前数据是否被篡改 当前区块的previousHash是否等于它的previous的hash值
    validateChain()

        // 验证祖先区块数据是否被篡改
        if(this.chain.length===1)
            if(this.chain[0].hash !== this.chain[0].computeHash())
                return false
            
            return true
        

        // 验证其他区块
        for(let i = 1, len = this.chain.length-1; i <= len; i++)
            const blockToValidate = this.chain[i]
            // 验证数据是否被篡改
            if(blockToValidate.hash !== blockToValidate.computeHash())
                console.log("数据被篡改！")
                return false
            
            // 验证hash值
            if(blockToValidate.previousHash !== this.chain[i-1].hash)
                console.log("前后区块断裂！")
                return false
            
        
        return true
    



const zzBlock = new Block('转账1000')
const zzBlock2 = new Block('转账3210')
const zzBlock3 = new Block('转账210')
const blockChain = new Chain()
blockChain.addBlockToChain(zzBlock)
blockChain.addBlockToChain(zzBlock2)
blockChain.addBlockToChain(zzBlock3)
console.log(blockChain.chain.length)

//尝试篡改数据
blockChain.chain[1].data = '转账10W'
blockChain.chain[1].mine(4)
console.log(blockChain)
console.log(blockChain.validateChain())