api/docs/rpc-core/README.md

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@polkadot/api
=============

This library provides a clean wrapper around all the methods exposed by a Polkadot network client.

Usage
-----

Installation -

```
npm install --save @polkadot/rpc-core
```

Initialisation -

```js
import Api from '@polkadot/rpc-core';
import WsProvider from '@polkadot/rpc-provider/ws';

const provider = new WsProvider('http://127.0.0.1:9944');
const api = new Api(provider);
```

Making calls -

```js
api.chain
  .getHeader('0x1234567890')
  .then((header) => console.log(header))
  .catch((error) => console.error(error));
```

Retrieving the best block (once-off) -

```js
api.chain
  .getHead()
  .then((headerHash) => {
    return api.chain.getHeader(headerHash);
  })
  .then((header) => {
    console.log(`best #${header.number.toString()}`);
  })
  .catch((error) => {
    console.error('error:', error);
  });
```

Retrieving best header via subscription -

```js
api.chain
  .newHead((error, header) => {
    if (error) {
      console.error('error:', error);
    }

    console.log(`best #${header.number.toString()}`);
  })
  .then((subscriptionId) => {
    // id for the subscription, can unsubscribe via
    // api.chain.newHead.unsubscribe(subscriptionId)
  })
  .catch((error) => {
    console.error('error subscribing:', error);
  });
```