我正在尝试通过使用JavaScript构建一个小项目来了解有关区块链的更多信息。任何人都可以向我解释为什么当我在console.log测试区块链上登录时为何不显示previousHash吗?
(npm install-如果需要SHA256可以保存crypto-js)
const SHA256 = require('crypto-js/sha256');
class Block{
//Index: (Optional) tells us where the block is in the chain
//Timestamp: tells us when the block was created
//Data: Can include any kind of data; for a currency you could store details of the transaction(transfer amount, sender id, receiver id)
//previousHash: String which contains the hash of the block which came before it (Ensures data integrity)
constructor(index, timestamp, data, previousHash = ''){
this.index = index;
this.timestamp = timestamp;
this.data = data;
this.previousHash = previousHash;
//Hash of this block
this.hash = this.calculateHash();
}
//Runs values from block through a hashing function to create a hash
calculateHash(){
return SHA256(this.index + this.previousHash + this.timestamp + JSON.stringify(this.data)).toString();
}
}
//8.44
class Blockchain{
//Initializes blockchain
constructor(){
this.chain = [this.createGenesisBlock];
}
// first block needs to be created manually
//index, timeStamp, data, previousHash(there is none in this case)
createGenesisBlock(){
return new Block(0, "01/01/2017", "Genesis block", "0");
}
//Returns most recently added block
getLatestBlock(){
return this.chain[this.chain.length -1];
}
//adds a new block to the chain
addBlock(newBlock){
newBlock.previousHash = this.getLatestBlock().hash;
newBlock.hash = newBlock.calculateHash
//The chain is just an array so you can use regular array methods
this.chain.push(newBlock);
}
}
//create instance of blockchhain
let Coin = new Blockchain();
Coin.addBlock(new Block(1, "10/07/2017", {amount: 4}));
Coin.addBlock(new Block(2, "12/07/2017", {amount: 10}));
console.log(JSON.stringify(Coin, null, 4));
我希望console.logged JSON文件包含previousHash以及索引,时间戳和数据。它包含除previousHash之外的所有内容。
感谢您的帮助,一直试图弄清楚我的头...
最佳答案
您在以下行中忘记了括号:this.chain = [this.createGenesisBlock()];
行,因此链的第一个元素将是对函数的引用,而不是Block
的实例。添加parathethen,它应该工作。
此外,您还忘记了在另一个函数调用中的括号:当您尝试调用函数newBlock.hash = newBlock.calculateHash()
时