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用uniapp，写区块链的例子

好的，下面是一个简单的区块链示例，使用uniapp框架和JavaScript编写：

1. 创建区块链类

```

class Block {

  constructor(index, timestamp, data, previousHash = '') {

    this.index = index;

    this.timestamp = timestamp;

    this.data = data;

    this.previousHash = previousHash;

    this.hash = this.calculateHash();

  }

  calculateHash() {

    return SHA256(this.index + this.previousHash + this.timestamp + JSON.stringify(this.data)).toString();

  }

}

class Blockchain {

  constructor() {

    this.chain = [this.createGenesisBlock()];

  }

  createGenesisBlock() {

    return new Block(0, "01/01/2021", "Genesis block", "0");

  }

  getLatestBlock() {

    return this.chain[this.chain.length - 1];

  }

  addBlock(newBlock) {

    newBlock.previousHash = this.getLatestBlock().hash;

    newBlock.hash = newBlock.calculateHash();

    this.chain.push(newBlock);

  }

  isChainValid() {

    for (let i = 1; i < this.chain.length; i++) {

      const currentBlock = this.chain[i];

      const previousBlock = this.chain[i - 1];

      if (currentBlock.hash !== currentBlock.calculateHash()) {

        return false;

      }

      if (currentBlock.previousHash !== previousBlock.hash) {

        return false;

      }

    }

    return true;

  }

}

```

2. 创建区块链实例并添加区块

```

let myCoin = new Blockchain();

myCoin.addBlock(new Block(1, "02/01/2021", { amount: 4 }));

myCoin.addBlock(new Block(2, "03/01/2021", { amount: 8 }));

```

3. 验证区块链是否有效

```

console.log('Is blockchain valid? ' + myCoin.isChainValid());

```

这是一个简单的区块链示例，可以在uniapp中进行测试和修改。需要注意的是，这只是一个基础示例，实际的区块链应该包含更多的功能和安全措施。