# Web3 provider

## **Web3 Provider**

Authereum is available as a Web3 provider.

Initialize the Authereum SDK and pass the provider to Web3:

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('kovan')

const provider = authereum.getProvider()
const web3 = new Web3(provider)
```

**Alternatively**, the Authereum provider can be initialized directly.

```javascript
import { AuthereumProvider } from 'authereum'
import Web3 from 'web3'

const provider = new AuthereumProvider('kovan')
const web3 = new Web3(provider)
```

### **Switch Networks**

To switch networks, the provider will need to be reinitialized with the network name:

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const networkName = 'rinkeby'
const authereum = new Authereum(networkName)

const provider = authereum.getProvider()
const web3 = new Web3(provider)
```

### **MetaMask and Web3 Browsers**

Use web3 injected provider is available or use Authereum's web3 provider:

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

let web3 

if (window.ethereum) {
    web3 = new Web3(window.ethereum)
} else if (window.web3) {
    web3 = new Web3(window.web3.currentProvider)
} else {
    const authereum = new Authereum('kovan')
    web3 = new Web3(authereum.getProvider())
}

const accounts = await web3.eth.getAccounts()
console.log(accounts[0])
```

### **Using Script Tags**

Using Web3 and Authereum libraries from CDNs and injecting web3 and the provider into the global window object:

```markup
<script src="https://cdn.jsdelivr.net/gh/ethereum/web3.js@1.0.0-beta.34/dist/web3.min.js"></script>
<script src="https://unpkg.com/authereum@latest/authereum.js"></script>
<script>
  const authereum = new Authereum('mainnet')
  const provider = authereum.getProvider()
  
  window.ethereum = provider
  window.web3 = new Web3(provider)
</script>
```

### **Provider Options**

See the[ Authereum SDK guide](https://docs.authereum.com/sdk) to see the options available.

## **Examples**

### **Logging in**

&#x20;Call the enable method on the provider to login:

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('kovan')
const provider = authereum.getProvider()
const web3 = new Web3(provider)

await provider.enable()

// Alternatively
// await web3.currentProvider.enable()
```

### **Logging out**

&#x20;Call the disable method on the provider to logout:

```javascript
const authereum = new Authereum('kovan')
const provider = authereum.getProvider()
const web3 = new Web3(provider)

await provider.disable()

// Alternatively
// await web3.currentProvider.disable()
```

### **Is Connected**

Check if user is connected to dapp.

```javascript
const authereum = new Authereum('kovan')
const provider = authereum.getProvider()
const web3 = new Web3(provider)

const isConnected = provider.isConnected()

console.log(isConnected)
```

### **Get Accounts**

Get connected account address:

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('kovan')
const web3 = new Web3(authereum.getProvider())

const accounts = await web3.eth.getAccounts()
console.log(accounts[0])

// Alternatively
// const account = await web3.eth.getCoinbase()
// console.log(account)
```

### **Get Balance**

&#x20;Reading the account ETH balance:

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('kovan')
const web3 = new Web3(authereum.getProvider())

const accounts = await web3.eth.getAccounts()
const balance = await web3.eth.getBalance(accounts[0])
console.log(balance)
```

### Detecting Authereum web3 provider

Example of how to check if web3 provider is an Authereum provider:

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('kovan')
const provider = authereum.getProvider()
const web3 = new Web3(provider)

console.log(provider.isAuthereum)

// Alternatively
// console.log(web3.currentProvider.isAuthereum)
```

### Sign Message

Example of how to sign a message:

```javascript
import Authereum from 'authereum'

const authereum = new Authereum('kovan')
const provider = authereum.getProvider()
  
const account = (await provider.getAccounts())[0]
const message = 'hello world'
const signature = await web3.eth.sign(message, account)
console.log(signature)
```

### Sign Personal Message

Example of how to sign a personal message:

```javascript
import Authereum from 'authereum'

const authereum = new Authereum('kovan')
const provider = authereum.getProvider()
  
const account = (await provider.getAccounts())[0]
const message = 'hello world'
const signature = await web3.eth.personal.sign(message, account)
console.log(signature)
```

### Sign Typed Data

Example of how to sign typed data using [EIP-712](https://github.com/ethereum/EIPs/blob/master/EIPS/eip-712.md):

```javascript
import Authereum from 'authereum'

const authereum = new Authereum('kovan')
const provider = authereum.getProvider()
  
const from = (await provider.getAccounts())[0]
const payload = [
   {
     type: 'string',
     name: 'username',
     value: 'alice'
   },
   {
     type: 'uint32',
     name: 'userId',
     value: '12345'
   }
 ]


const params = [payload, from]
const method = 'eth_signTypedData'

provider.sendAsync({
  id: 1,
  method,
  params,
  from
}, (error, res) => {
  if (error) throw error
  console.log(res.result)
})
```

### Sign Transaction

Example of how to sign a transaction:

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('mainnet')
const provider = authereum.getProvider()
const web3 = new Web3(provider)

const tx = {
  to: '0x22d491Bde2303f2f43325b2108D26f1eAbA1e32b',
  value: '10000000000000000'
}

const { raw } = await web3.eth.signTransaction(tx)
const transactionHash = web3.utils.sha3(raw)

console.log(transactionHash)
```

### Send Transaction

Example of how to send a transaction:

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('mainnet')
const provider = authereum.getProvider()
const web3 = new Web3(provider)

const tx = {
  to: '0x22d491Bde2303f2f43325b2108D26f1eAbA1e32b',
  value: '10000000000000000'
}

const { transactionHash } = await web3.eth.sendTransaction(tx)

console.log(transactionHash)
```

### Send Transaction Batch

Example of how to send a transaction batch (2 ETH transfers):

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('mainnet')
const provider = authereum.getProvider()
const web3 = new Web3(provider)

const txs = [
  {
    to: '0x22d491Bde2303f2f43325b2108D26f1eAbA1e32b',
    value: '10000000000000000',
    gasLimit: '1000000'
  }, {
    to: '0x22d491Bde2303f2f43325b2108D26f1eAbA1e32b',
    value: '10000000000000000',
    gasLimit: '1000000'
  }
]

const { transactionHash } = await provider.sendTransactionBatch(txs)

console.log(transactionHash)
```

Example of how to send a transaction batch (DAI approve and transferFrom):

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('mainnet')
const provider = authereum.getProvider()
const web3 = new Web3(provider)

const txs = [
  // Approve
  {
    to: '0x6B175474E89094C44Da98b954EedeAC495271d0F',
    value: '0',
    gasLimit: '1000000',
    data: '0x095ea7b3000000000000000000000000e4c9194962532feb467dce8b3d42419641c6ed2e0000000000000000000000000000000000000000000000008c4cb6a94641cfbd'
  },
  // transferFrom
  {
    to: '0x6B175474E89094C44Da98b954EedeAC495271d0F',
    value: '0',
    gasLimit: '1000000',
    data: '0x23b872dd0000000000000000000000003b18c73ed8ff086695b6b9b314843dfde9fad1c600000000000000000000000018d3d5d945353f46f0f5ca7b808c8a6443e6cbb40000000000000000000000000000000000000000000000008c4cb6a94641cfbd'
  }
]

const { transactionHash } = await provider.sendTransactionBatch(txs)

console.log(transactionHash)
```

### Estimate Gas Batch

Example of how to estimate a transaction batch (2 ETH transfers):

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('mainnet')
const provider = authereum.getProvider()
const web3 = new Web3(provider)

const txs = [
  {
    to: '0x22d491Bde2303f2f43325b2108D26f1eAbA1e32b',
    value: '10000000000000000'
  }, {
    to: '0x22d491Bde2303f2f43325b2108D26f1eAbA1e32b',
    value: '10000000000000000'
  }
]

const { transactionHash } = await provider.estimateGasBatch(txs)

console.log(transactionHash) // [17894, 11845]
```

Example of how to estimate a transaction batch (DAI approve and transferFrom):

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('mainnet')
const provider = authereum.getProvider()
const web3 = new Web3(provider)

const txs = [
  // Approve
  {
    to: '0x6B175474E89094C44Da98b954EedeAC495271d0F',
    value: '0',
    data: '0x095ea7b3000000000000000000000000e4c9194962532feb467dce8b3d42419641c6ed2e0000000000000000000000000000000000000000000000008c4cb6a94641cfbd'
  },
  // transferFrom
  {
    to: '0x6B175474E89094C44Da98b954EedeAC495271d0F',
    value: '0',
    data: '0x23b872dd0000000000000000000000003b18c73ed8ff086695b6b9b314843dfde9fad1c600000000000000000000000018d3d5d945353f46f0f5ca7b808c8a6443e6cbb40000000000000000000000000000000000000000000000008c4cb6a94641cfbd'
  }
]

const { transactionHash } = await provider.estimateGasBatch(txs)

console.log(transactionHash) // [10955,7057]
```

### ERC20: Token Balance

Example of how to read token balance:

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('mainnet')
const provider = authereum.getProvider()
const web3 = new Web3(provider)

const abi = [{
    "constant": true,
    "inputs": [
        {
            "name": "_owner",
            "type": "address"
        }
    ],
    "name": "balanceOf",
    "outputs": [
        {
            "name": "balance",
            "type": "uint256"
        }
    ],
    "payable": false,
    "stateMutability": "view",
    "type": "function"
}]

const token = '0x89d24a6b4ccb1b6faa2625fe562bdd9a23260359'
const instance = await new web3.eth.Contract(abi, token)

const account = '0x22d491Bde2303f2f43325b2108D26f1eAbA1e32b'
const amount = await instance.methods.balanceOf(account).call()

console.log(amount)
```

### ERC20: Token Allowance

Example of how to read token allowance:

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('mainnet')
const provider = authereum.getProvider()
const web3 = new Web3(provider)

const abi = [{
    "constant": true,
    "inputs": [
        {
            "name": "_owner",
            "type": "address"
        },
        {
            "name": "_spender",
            "type": "address"
        }
    ],
    "name": "allowance",
    "outputs": [
        {
            "name": "",
            "type": "uint256"
        }
    ],
    "payable": false,
    "stateMutability": "view",
    "type": "function"
}]

const token = '0x89d24a6b4ccb1b6faa2625fe562bdd9a23260359'
const instance = await new web3.eth.Contract(abi, token)

const owner = (await web3.eth.getAccounts())[0]
const spender = '0x22d491Bde2303f2f43325b2108D26f1eAbA1e32b'
const allowance = await instance.methods.allowance(owner, spender).call()

console.log(allowance)
```

### ERC20: Token Approve

Example of how to do a token approve call:

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('mainnet')
const provider = authereum.getProvider()
const web3 = new Web3(provider)

const abi = [{
    "constant": false,
    "inputs": [
        {
            "name": "_spender",
            "type": "address"
        },
        {
            "name": "_value",
            "type": "uint256"
        }
    ],
    "name": "approve",
    "outputs": [
        {
            "name": "",
            "type": "bool"
        }
    ],
    "payable": false,
    "stateMutability": "nonpayable",
    "type": "function"
}]

const token = '0x89d24a6b4ccb1b6faa2625fe562bdd9a23260359'
const instance = await new web3.eth.Contract(abi, token)

const from = (await web3.eth.getAccounts())[0]
const spender = '0x22d491Bde2303f2f43325b2108D26f1eAbA1e32b'
const value = '1000000000000000000'
const { transactionHash } = await instance.methods.approve(spender, value).send({ from })

console.log(transactionHash)
```

### ERC20: Token Transfer

Example of how to do a token transfer call:

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('mainnet')
const provider = authereum.getProvider()
const web3 = new Web3(provider)

const abi = [{
    "constant": false,
    "inputs": [
        {
            "name": "_to",
            "type": "address"
        },
        {
            "name": "_value",
            "type": "uint256"
        }
    ],
    "name": "transfer",
    "outputs": [
        {
            "name": "",
            "type": "bool"
        }
    ],
    "payable": false,
    "stateMutability": "nonpayable",
    "type": "function"
}]

const token = '0x89d24a6b4ccb1b6faa2625fe562bdd9a23260359'
const instance = await new web3.eth.Contract(abi, token)

const from = (await web3.eth.getAccounts())[0]
const to = '0x22d491Bde2303f2f43325b2108D26f1eAbA1e32b'
const value = '1000000000000000000'
const { transactionHash } = await instance.methods.transfer(to, value).send({ from })

console.log(transactionHash)
```

### ERC20: Token Transfer From

Example of how to do a token transfer from call:

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('mainnet')
const provider = authereum.getProvider()
const web3 = new Web3(provider)

const abi = [{
    "constant": false,
    "inputs": [
        {
            "name": "_from",
            "type": "address"
        },
        {
            "name": "_to",
            "type": "address"
        },
        {
            "name": "_value",
            "type": "uint256"
        }
    ],
    "name": "transferFrom",
    "outputs": [
        {
            "name": "",
            "type": "bool"
        }
    ],
    "payable": false,
    "stateMutability": "nonpayable",
    "type": "function"
}]

const token = '0x89d24a6b4ccb1b6faa2625fe562bdd9a23260359'
const instance = await new web3.eth.Contract(abi, token)

const from = (await web3.eth.getAccounts())[0]
const to = '0x22d491Bde2303f2f43325b2108D26f1eAbA1e32b'
const value = '1000000000000000000'
const { transactionHash } = await instance.methods.transferFrom(from, to, value).send({ from })

console.log(transactionHash)
```

### ERC721: Owner Of

Example of how to check owner of NFT:

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('mainnet')
const provider = authereum.getProvider()
const web3 = new Web3(provider)

const abi = [{
    "constant": true,
    "inputs": [
        {
            "name": "tokenId",
            "type": "uint256"
        }
    ],
    "name": "ownerOf",
    "outputs": [
        {
            "name": "",
            "type": "address"
        }
    ],
    "payable": false,
    "stateMutability": "view",
    "type": "function"
}]

const token = '0x6EbeAf8e8E946F0716E6533A6f2cefc83f60e8Ab'
const instance = await new web3.eth.Contract(abi, token)

const tokenId = '580767'
const owner = await instance.methods.ownerOf(tokenId).call()

console.log(owner)
```

### ERC721: Get Approved

Example of how to check if NFT is approved:

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('mainnet')
const provider = authereum.getProvider()
const web3 = new Web3(provider)

const abi = [{
    "constant": true,
    "inputs": [
        {
            "name": "tokenId",
            "type": "uint256"
        }
    ],
    "name": "getApproved",
    "outputs": [
        {
            "name": "",
            "type": "address"
        }
    ],
    "payable": false,
    "stateMutability": "view",
    "type": "function"
}]

const token = '0x6EbeAf8e8E946F0716E6533A6f2cefc83f60e8Ab'
const instance = await new web3.eth.Contract(abi, token)

const tokenId = '580767'
const to = await instance.methods.getApproved(tokenId).call()

console.log(to)
```

### ERC721: Approve

Example of how to do a NFT approve call:

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('mainnet')
const provider = authereum.getProvider()
const web3 = new Web3(provider)

const abi = [{
    "constant": false,
    "inputs": [
        {
            "name": "to",
            "type": "address"
        },
        {
            "name": "tokenId",
            "type": "uint256"
        }
    ],
    "name": "approve",
    "outputs": [],
    "payable": false,
    "stateMutability": "nonpayable",
    "type": "function"
}]

const token = '0x06012c8cf97bead5deae237070f9587f8e7a266d'
const instance = await new web3.eth.Contract(abi, token)

const from = (await web3.eth.getAccounts())[0]
const to = '0x6EbeAf8e8E946F0716E6533A6f2cefc83f60e8Ab'
const tokenId = '580767'
const { transactionHash } = await instance.methods.approve(to, tokenId).send({ from })

console.log(transactionHash)
```

### ERC721: Transfer

Example of how to do a NFT transfer call:

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('mainnet')
const provider = authereum.getProvider()
const web3 = new Web3(provider)

const abi = [{
  "constant": false,
  "inputs": [
    {
      "name": "to",
      "type": "address"
    },
    {
      "name": "tokenId",
      "type": "uint256"
    }
  ],
  "name": "transfer",
  "outputs": [],
  "payable": false,
  "stateMutability": "nonpayable",
  "type": "function"
}]

const token = '0x06012c8cf97bead5deae237070f9587f8e7a266d'
const instance = await new web3.eth.Contract(abi, token)

const from = (await web3.eth.getAccounts())[0]
const to = '0x22d491Bde2303f2f43325b2108D26f1eAbA1e32b'
const tokenId = '1667849'
const { transactionHash } = await instance.methods.transfer(from, to, tokenId).send({ from })

console.log(transactionHash)
```

### ERC721: Transfer From

Example of how to do a NFT transfer from call:

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('mainnet')
const provider = authereum.getProvider()
const web3 = new Web3(provider)

const abi = [{
    "constant": false,
    "inputs": [
        {
            "name": "from",
            "type": "address"
        },
        {
            "name": "to",
            "type": "address"
        },
        {
            "name": "tokenId",
            "type": "uint256"
        }
    ],
    "name": "transferFrom",
    "outputs": [],
    "payable": false,
    "stateMutability": "nonpayable",
    "type": "function"
}]

const token = '0x6EbeAf8e8E946F0716E6533A6f2cefc83f60e8Ab'
const instance = await new web3.eth.Contract(abi, token)

const from = (await web3.eth.getAccounts())[0]
const to = '0x22d491Bde2303f2f43325b2108D26f1eAbA1e32b'
const tokenId = '580767'
const { transactionHash } = await instance.methods.transferFrom(from, to, tokenId).send({ from })

console.log(transactionHash)
```

### ERC721: Safe Transfer From

Example of how to do a NFT safe transfer from call:

```javascript
import Authereum from 'authereum'
import Web3 from 'web3'

const authereum = new Authereum('mainnet')
const provider = authereum.getProvider()
const web3 = new Web3(provider)

const abi = [{
    "constant": false,
    "inputs": [
        {
            "name": "from",
            "type": "address"
        },
        {
            "name": "to",
            "type": "address"
        },
        {
            "name": "tokenId",
            "type": "uint256"
        }
    ],
    "name": "transferFrom",
    "outputs": [],
    "payable": false,
    "stateMutability": "nonpayable",
    "type": "function"
}]

const token = '0x6EbeAf8e8E946F0716E6533A6f2cefc83f60e8Ab'
const instance = await new web3.eth.Contract(abi, token)

const from = (await web3.eth.getAccounts())[0]
const to = '0x22d491Bde2303f2f43325b2108D26f1eAbA1e32b'
const tokenId = '580767'
const data = '0x00'
const { transactionHash } = await instance.methods.safeTransferFrom(from, to, tokenId, data).send({ from })

console.log(transactionHash)
```

### Validating Signatures (ecrecover)

See the [Verifying Signatures](https://docs.authereum.com/verifying-signatures) page.