├── README.md
└── main.js


/README.md:
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1 | # js-blockchain-pt1


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/main.js:
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 1 | const SHA256 = require('crypto-js/sha256')
 2 | 
 3 | class Block {
 4 |     constructor(index, timestamp, data, previousHash) {
 5 |         this.index = index;
 6 |         this.timestamp = timestamp;
 7 |         this.data = data;
 8 |         this.previousHash = previousHash;
 9 |         this.hash = this.calculateHash();
10 |         this.nonce = 0;
11 |     }
12 | 
13 |     calculateHash() {
14 |         return SHA256(this.index + this.previousHash + this.timestamp + this.data + this.nonce).toString();
15 |     }
16 | 
17 |     mineBlock(difficulty) {
18 | 
19 |     }
20 | }
21 | 
22 | class Blockchain{
23 |     constructor() {
24 |         this.chain = [this.createGenesis()];
25 |     }
26 | 
27 |     createGenesis() {
28 |         return new Block(0, "01/01/2017", "Genesis block", "0")
29 |     }
30 | 
31 |     latestBlock() {
32 |         return this.chain[this.chain.length - 1]
33 |     }
34 | 
35 |     addBlock(newBlock){
36 |         newBlock.previousHash = this.latestBlock().hash;
37 |         newBlock.hash = newBlock.calculateHash();
38 |         this.chain.push(newBlock);
39 |     }
40 | 
41 |     checkValid() {
42 |         for(let i = 1; i < this.chain.length; i++) {
43 |             const currentBlock = this.chain[i];
44 |             const previousBlock = this.chain[i - 1];
45 | 
46 |             if (currentBlock.hash !== currentBlock.calculateHash()) {
47 |                 return false;
48 |             }
49 | 
50 |             if (currentBlock.previousHash !== previousBlock.hash) {
51 |                 return false;
52 |             }
53 |         }
54 | 
55 |         return true;
56 |     }
57 | }
58 | 
59 | let jsChain = new Blockchain();
60 | jsChain.addBlock(new Block("12/25/2017", {amount: 5}));
61 | jsChain.addBlock(new Block("12/26/2017", {amount: 10}));
62 | 
63 | 
64 | console.log(JSON.stringify(jsChain, null, 4));
65 | console.log("Is blockchain valid? " + jsChain.checkValid());


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