javascript - 为什么当我 console.log 我的测试区 block 链时 previousHash 没有显示？

Question

我正在尝试通过使用 JavaScript 构建一个小项目来了解更多关于区 block 链的信息。谁能向我解释为什么当我对测试区 block 链进行 console.log 时 previousHash 不显示？

(npm install --save crypto-js 如果你需要 SHA256)

        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，我绞尽脑汁想弄清楚这个问题......

Answer 1

您忘记了行中的括号: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。添加括号，它应该可以工作。

此外，您还忘记了另一个函数调用中的括号:当您尝试调用函数 newBlock.hash = newBlock.calculateHash()