# Block

A Block instance represents the information on a block in the bitcoin network. Instantiating it is not a cheap operation, as the tree of transactions needs to be created or verified. There's a (BlockHeader)[https://github.com/bitpay/bitcore/tree/master/lib/blockheader.js] interface that is easier on the javascript VM.

Given a hexa or base64 string representation of the serialization of a block with its transactions, you can instantiate a Block instance. It will calculate and check the merkle root hash (if enough data is provided), but transactions won't necessarily be valid spends, and this class won't validate them. A binary representation as a `Buffer` instance is also valid input for a Block's constructor.

```javascript
assert(Block.isValidHeader(data);
assert(Block.isValidBlock(data);

var block = new Block(hexaEncodedBlock);
assert(block.id && block.hash && block.id === block.hash);
assert(block.version === Block.CurrentVersion);
assert(block.prevHash);
assert(block.timestamp);
assert(block.nonce);
assert(block.size);
assert(block.transactions[0] instanceof Transaction);
```

## Navigating through transactions

The set of transactions in a block can be explored by iterating on the block's
`transactions` member.

```javascript
for (var transaction in block.transactions) {
  // ...
}
```