简单BlockChain程序

Question

我正在尝试构建这个简单的" blockchain“代码，我在网上发现它是为了让我更好地理解区块链技术。

但是当我运行它时，它会给我一个错误，当它运行。

这就是我得到的错误：-

从‘区块链’导入{BlockChain}；^

SyntaxError:意外令牌

类块

 export class  Block{

    constructor(timestamp, data, previousHash = '') {
        this.timestamp = timestamp;
        this.data = data;
        this.previousHash = previousHash;
        // The calculation of the hash must be at the end so to ensure that all data is assigned correctly before calculation
        this.hash = this.calculateHash(); }

    calculateHash() {
        return SHA256(this.previousHash + this.timestamp + JSON.stringify(this.data)).toString();
    }
}

类BlockChain

import {Block} from 'Block';



  export class  BlockChain {

    constructor() {
        this.chain = [this.createGenesisBlock()];
    }

    createGenesisBlock(){
        return new Block("2018-11-11 00:00:00", "Genesis block of simple chain", "");
    }

    getLatestBlock() {
        return this.chain[this.chain.length - 1];
    }

    addBlock(newBlock) {
        // The previous hash value of the new block is the hash value of the last block of the existing blockchain；
        newBlock.previousHash = this.getLatestBlock().hash;
        // Recalculate the hash value of the new block (because the previousHash is specified)；
        newBlock.hash = newBlock.calculateHash();
        //Add new blocks to the chain；
        this.chain.push(newBlock);
    }

    isChainValid() {
        //Traverse all the blocks
        for (let i = 1; i < this.chain.length; i++) {
            const currentBlock = this.chain[i];
            const previousBlock = this.chain[i - 1];
            //Recalculate the has value of the current block. If the hash value is not matched, it indicates that data of the block was changed without permission, and therefore the has value is not recalculated.
            if (currentBlock.hash !== currentBlock.calculateHash()) {
                console.error("hash not equal: " + JSON.stringify(currentBlock));
                return false;
            }
            // Determine whether the previousHash of the current block is equal to the hash of the previous block. If they are not equal to each other, this means that the previous block was changed without permission. Although the hash value is recalculated correctly, the hash value of the subsequent block is not recalculated, resulting the the whole chain breaking.
            if (currentBlock.previousHash !== previousBlock.calculateHash) {
                console.error("previous hash not right: " + JSON.stringify(currentBlock));
                return false;
            }
        }
        return true;
    }

}

类测试

import {BlockChain} from 'BlockChain';
import {Block} from 'Block';



    let simpleChain = new BlockChain();

    simpleChain.addBlock(new Block("2018-11-11 00:00:01", {amount: 10}));
    simpleChain.addBlock(new Block("2018-11-11 00:00:02", {amount: 20}));


    console.log(JSON.stringify(simpleChain, null, 4));

    console.log("is the chain valid? " + simpleChain.isChainValid());

Answer 1

密码没问题。您可以按以下方式运行代码：

1. 使用Node:

安装加密js

npm安装密码js

从命令window/Terminal:打开

1. 节点提示符

节点

1. 打开Node:

中的编辑器

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1. 需要sha256模块。将以下代码粘贴到编辑器中：

const SHA256 =需要量(‘crypto/sha256’)；

1. 在编辑器：

中粘贴块、BlockChain和测试类

类块

class  Block{

    constructor(timestamp, data, previousHash = '') {
        this.timestamp = timestamp;
        this.data = data;
        this.previousHash = previousHash;
        // The calculation of the hash must be at the end so to ensure that all data is assigned correctly before calculation
        this.hash = this.calculateHash(); }

    calculateHash() {
        return SHA256(this.previousHash + this.timestamp + JSON.stringify(this.data)).toString();
    }
}

类BlockChain

class  BlockChain {

    constructor() {
        this.chain = [this.createGenesisBlock()];
    }

    createGenesisBlock(){
        return new Block("2018-11-11 00:00:00", "Genesis block of simple chain", "");
    }

    getLatestBlock() {
        return this.chain[this.chain.length - 1];
    }

    addBlock(newBlock) {
        // The previous hash value of the new block is the hash value of the last block of the existing blockchain；
        newBlock.previousHash = this.getLatestBlock().hash;
        // Recalculate the hash value of the new block (because the previousHash is specified)；
        newBlock.hash = newBlock.calculateHash();
        //Add new blocks to the chain；
        this.chain.push(newBlock);
    }

    isChainValid() {
        //Traverse all the blocks
        for (let i = 1; i < this.chain.length; i++) {
            const currentBlock = this.chain[i];
            const previousBlock = this.chain[i - 1];
            //Recalculate the has value of the current block. If the hash value is not matched, it indicates that data of the block was changed without permission, and therefore the has value is not recalculated.
            if (currentBlock.hash !== currentBlock.calculateHash()) {
                console.error("hash not equal: " + JSON.stringify(currentBlock));
                return false;
            }
            // Determine whether the previousHash of the current block is equal to the hash of the previous block. If they are not equal to each other, this means that the previous block was changed without permission. Although the hash value is recalculated correctly, the hash value of the subsequent block is not recalculated, resulting the the whole chain breaking.
            if (currentBlock.previousHash !== previousBlock.calculateHash) {
                console.error("previous hash not right: " + JSON.stringify(currentBlock));
                return false;
            }
        }
        return true;
    }

}

类测试

let simpleChain = new BlockChain();

    simpleChain.addBlock(new Block("2018-11-11 00:00:01", {amount: 10}));
    simpleChain.addBlock(new Block("2018-11-11 00:00:02", {amount: 20}));


    console.log(JSON.stringify(simpleChain, null, 4));

    console.log("is the chain valid? " + simpleChain.isChainValid());

1. 按^D完成

这将为您提供以下输出：

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