Cookbook for viewing block extrinsics (#2476)

Author: jacogr

docs/cookbook/blocks.md

@@ -42,3 +42,20 @@ const header = await api.derive.chain.getHeader();
 
 console.log(`#${header.number}: ${header.author}`);
 ```
+
+## How do I view block extrinsic information?
+
+The transactions are included in a signed block as part of the extrinsics - some of these will be unsigned and generated by the block author and some of these may be submitted from external sources and be signed. (Some palettes do use unsigned transactions, so signed/unsigned is not an indication of origin). To retrieve the block and display the transaction information, we can do the following -
+
+```js
+// no blockHash is specified, so we retrieve the latest
+const signedBlock = await this.api.rpc.chain.getBlock();
+
+// the information for each of the contained extrinsics
+signedBlock.block.extrinsics.forEach((ex, index) => {
+  // the extrinsics are decoded by the API
+  console.log(index, ex.toHuman());
+});
+```
+
+In the above `.toHuman()` is used to format into a human-readable representation. You can inspect/extract specific fields from the decoded extrinsic as required, for instance `ex.method.section` would return the pallete that executed this transaction.