Chain Validation:
javascript

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;
}

Use this to detect tampering or divergence in nodes.

🧠 Summary:
You’ve built a working blockchain model in JavaScript.

You added transaction logic and mining simulation.

You now understand the basics of a consensus algorithm.

📝 Workbook Activities:
Customize your Transaction class with sender info.

Add your data to a block and test integrity.

Simulate tampering and run isChainValid() to detect it.

Research how PoS or other consensus models might be implemented.