├── .gitignore
├── block.js
├── blockchain.js
├── index.js
├── package-lock.json
└── package.json


/.gitignore:
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1 | node_modules


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/block.js:
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 1 | const sha256 = require('crypto-js/sha256')
 2 | 
 3 | class Block {
 4 |     constructor(index = 0, previousHash = null, data = 'Genesis block', difficulty = 1) {
 5 |         this.index = index
 6 |         this.previousHash = previousHash
 7 |         this.data = data
 8 |         this.timestamp = new Date()
 9 |         this.difficulty = difficulty
10 |         this.nonce = 0
11 |         
12 |         this.mine()
13 |     }
14 | 
15 |     generateHash() {
16 |         return sha256(this.index + this.previousHash + JSON.stringify(this.data) + this.timestamp + this.nonce).toString()
17 |     }
18 | 
19 |     mine() {
20 |         this.hash = this.generateHash()
21 | 
22 |         while (!(/^0*$/.test(this.hash.substring(0, this.difficulty)))) {
23 |             this.nonce++
24 |             this.hash = this.generateHash()
25 |         }
26 |     }
27 | }
28 | 
29 | module.exports = Block


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/blockchain.js:
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 1 | const Block = require('./block')
 2 | 
 3 | class Blockchain {
 4 |     constructor(difficulty = 1) {
 5 |         this.blocks = [new Block()]
 6 |         this.index = 1
 7 |         this.difficulty = difficulty
 8 |     }
 9 | 
10 |     getLastBlock() {
11 |         return this.blocks[this.blocks.length - 1]
12 |     }
13 | 
14 |     addBlock(data) {
15 |         const index = this.index
16 |         const difficulty = this.difficulty
17 |         const previousHash = this.getLastBlock().hash
18 | 
19 |         const block = new Block(index, previousHash, data, difficulty)
20 | 
21 |         this.index++
22 |         this.blocks.push(block)
23 |     }
24 | 
25 |     isValid() {
26 |         for (let i = 1; i < this.blocks.length; i++) {
27 |             const currentBlock = this.blocks[i]
28 |             const previousBlock = this.blocks[i - 1]
29 | 
30 |             if (currentBlock.hash !== currentBlock.generateHash()) {
31 |                 return false
32 |             }
33 | 
34 |             if (currentBlock.index !== previousBlock.index + 1) {
35 |                 return false
36 |             }
37 | 
38 |             if (currentBlock.previousHash !== previousBlock.hash) {
39 |                 return false
40 |             }
41 |         }
42 |         return true
43 |     }
44 | }
45 | 
46 | module.exports = Blockchain


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/index.js:
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 1 | const Blockchain = require('./blockchain')
 2 | 
 3 | const blockchain = new Blockchain()
 4 | blockchain.addBlock({ amount: 4 })
 5 | blockchain.addBlock({ amount: 50 })
 6 | 
 7 | console.log(blockchain)
 8 | 
 9 | console.log(blockchain.isValid())
10 | blockchain.blocks[1].data.amount = 30000
11 | console.log(blockchain.isValid())


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/package-lock.json:
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 1 | {
 2 |   "name": "blockchain-javascript",
 3 |   "version": "1.0.0",
 4 |   "lockfileVersion": 1,
 5 |   "requires": true,
 6 |   "dependencies": {
 7 |     "crypto-js": {
 8 |       "version": "3.1.9-1",
 9 |       "resolved": "https://registry.npmjs.org/crypto-js/-/crypto-js-3.1.9-1.tgz",
10 |       "integrity": "sha1-/aGedh/Ad+Af+/3G6f38WeiAbNg="
11 |     }
12 |   }
13 | }
14 | 


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/package.json:
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 1 | {
 2 |   "name": "blockchain-javascript",
 3 |   "version": "1.0.0",
 4 |   "description": "",
 5 |   "main": "index.js",
 6 |   "scripts": {
 7 |     "test": "echo \"Error: no test specified\" && exit 1"
 8 |   },
 9 |   "author": "",
10 |   "license": "ISC",
11 |   "dependencies": {
12 |     "crypto-js": "^3.1.9-1"
13 |   }
14 | }
15 | 


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