# Providers API

A Provider abstracts a connection to the Ethereum blockchain, for issuing queries and sending state changing transactions.

Unlike the Web3 provider, there is no concept of accounts or signing entities in an Ethers Provider. It is simply a connection to the network, and cannot unlock accounts or sign and is unaware of your Ethereum addresses.

To manage state changing operations, you must use a Wallet to sign transactions. If you pass a wallet in as a signer to a Contract, this is managed for you by the contract.

## Connecting to Ethereum

There are several ways to connect to the Ethereum blockchain:

new ethers . providers . EtherscanProvider( [ network ] [ , apiToken ] )

  Connect to the Etherscan blockchain web service API.

  default: network=’homestead’, apiToken=null

new ethers . providers . JsonRpcProvider( [ url ] [ , network ] )

  Connect to the JSON-RPC API url of an Ethereum node, such as Parity or Geth.

  default: url=”http://localhost:8545/”, network=’homestead’

new ethers . providers . InfuraProvider( [ network ] [ , apiAccessToken ] )

  Connect to the INFURA hosted network of Ethereum nodes.

  default: network=’homestead’, apiAccessToken=null

new ethers . providers . Web3Provider( web3Provider [ , network ] )

  Connect to an existing Web3 provider (e.g. web3Instance.currentProvider).

  default: network=’homestead’

new ethers . providers . FallbackProvider( providers )
  Improves reliability by attempting each provider in turn, falling back to the next in the list if an error was encountered.
ethers . providers . getDefaultProvider( [ network ] )

  This automatically creates a FallbackProvider backed by INFURA and Etherscan; recommended

  default: network=’homestead’

### Examples

    var providers = require('ethers').providers;

    // Connect to Ropsten (the test network)

    // You may specify any of:
    // - boolean; true = ropsten, false = homestead
    // - object; { name: 'ropsten', chainId: 3 } (see ethers.networks);
    // - string; e.g. 'homestead', 'ropsten', 'rinkeby', 'kovan'
    var network = providers.networks.ropsten;

    // Connect to INFUA
    var infuraProvider = new providers.InfuraProvider(network);

    // Connect to Etherscan
    var etherscanProvider = new providers.EtherscanProvider(network);

    // Creating a provider to automatically fallback onto Etherscan
    // if INFURA is down
    var fallbackProvider = new providers.FallbackProvider([
        infuraProvider,
        etherscanProvider
    ]);

    // This is equivalent to using the getDefaultProvider
    var provider = providers.getDefaultProvider(network)

    // Connect to a local Parity instance
    var provider = new providers.JsonRpcProvider('http://localhost:8545', network);

    // Connect to an injected Web3's provider (e.g. MetaMask)
    var web3Provider = new providers.Web3Provider(web3.currentProvider, network);

## Prototype

All properties are immutable, and reflect their default value if not specified, or if indirectly populated by child Objects.

### Provider

prototype . name
  The name of the network the provider is connected to (e.g. ‘homestead’, ‘ropsten’, ‘rinkeby’, ‘kovan’)
prototype . chainId
  The chain ID (or network ID) this provider is connected as; this is used by signers to prevent replay attacks across compatible networks

### FallbackProvider ( inherits from Provider )

prototype . providers
  A copy of the array of providers (modifying this variable will not affect the providers attached)

### JsonRpcProvider ( inherits from Provider )

prototype . url
  The JSON-RPC URL the provider is connected to
prototype . send ( method , params )
  Send the JSON-RPC method with params. This is useful for calling non-standard or less common JSON-RPC methods. A Promise is returned which will resolve to the parsed JSON result.

### EtherscanProvider ( inherits from Provider )

prototype . apiToken
  The Etherscan API Token (or null if not specified)

### InfuraProvider ( inherits from JsonRpcProvider )

prototype . apiAccessToken
  The INFURA API Access Token (or null if not specified)

### Web3Provider ( inherits from JsonRpcProvider )

prototype . provider

  The underlying Web3-compatible provider from the Web3 library, for example an HTTPProvider or IPCProvider. The only required method on a Web3 provider is:

  sendAsync ( method , params , callback )

## Account Actions

prototype . getBalance ( addressOrName [ , blockTag ] )

  Returns a Promise with the balance (as a BigNumber) of addressOrName at blockTag. (See: Block Tags)

  default: blockTag=”latest”

prototype . getTransactionCount ( addressOrName [ , blockTag ] )

  Returns a Promise with the number of sent transactions (as a Number) from addressOrName at blockTag. This is also the nonce required to send a new transaction. (See: Block Tags)

  default: blockTag=”latest”

prototype . lookupAddress ( address )
  Returns a Promise which resolves to the ENS name (or null) that address resolves to.
prototype . resolveName ( ensName )
  Returns a Promise which resolves to the address (or null) of that the ensName resolves to.

### Examples

    var ethers = require('ethers');
    var providers = ethers.providers;

    var provider = providers.getDefaultProvider('ropsten');

    var address = "0x02F024e0882B310c6734703AB9066EdD3a10C6e0";

    provider.getBalance(address).then(function(balance) {

        // balance is a BigNumber (in wei); format is as a sting (in ether)
        var etherString = ethers.utils.formatEther(balance);

        console.log("Balance: " + etherString);
    });

    provider.getTransactionCount(address).then(function(transactionCount) {
        console.log("Total Transactions Ever Send: " + transactionCount);
    });

    provider.resolveName("test.ricmoose.eth").then(function(address) {
        console.log("Address: " + address);
    });

## Blockchain Status

prototype . getBlockNumber ( )
  Returns a Promise with the latest block number (as a Number).
prototype . getGasPrice ( )
  Returns a Promise with the current gas price (as a BigNumber).
prototype . getBlock ( blockHashOrBlockNumber )
  Returns a Promise with the block at blockHashorBlockNumber. (See: Block Responses)
prototype . getTransaction ( transactionHash )
  Returns a Promise with the transaction with transactionHash. (See: Transaction Responses)
prototype . getTransactionReceipt ( transactionHash )
  Returns a Promise with the transaction receipt with transactionHash. (See: Transaction Receipts)

### Examples

Current State

    var provider = providers.getDefaultProvider();

    provider.getBlockNumber().then(function(blockNumber) {
        console.log("Current block number: " + blockNumber);
    });

    provider.getGasPrice().then(function(gasPrice) {
        // gasPrice is a BigNumber; convert it to a decimal string
        gasPriceString = gasPrice.toString();

        console.log("Current gas price: " + gasPriceString);
    });

Blocks

    var provider = providers.getDefaultProvider();

    // Block Number
    provider.getBlock(3346773).then(function(block) {
        console.log(block);
    });

    // Block Hash
    var blockHash = "0x7a1d0b010393c8d850200d0ec1e27c0c8a295366247b1bd6124d496cf59182ad";
    provider.getBlock(blockHash).then(function(block) {
        console.log(block);
    });

Transactions

    var provider = providers.getDefaultProvider();

    var transactionHash = "0x7baea23e7d77bff455d94f0c81916f938c398252fb62fce2cdb43643134ce4ed";

    provider.getTransaction(transactionHash).then(function(transaction) {
        console.log(transaction);
    });

    provider.getTransactionReceipt(transactionHash).then(function(transactionReceipt) {
        console.log(transactionReceipt);
    });

## Ethereum Name Resolution

The Ethereum Naming Service (ENS) allows easy to remember and use names to be assigned to Ethereum addresses. Any provider operation which takes an address may also take an ENS name.

It is often useful to resolve a name entered by a user or perform a reverse lookup of an address to get a more human readbale name.

Resolving Names

    var providers = require('ethers').providers;
    var provider = providers.getDefaultProvider();
    provider.resolveName('registrar.firefly.eth').then(function(address) {
        console.log(address);
        // '0x6fC21092DA55B392b045eD78F4732bff3C580e2c'
    });

Looking up Addresses

    provider.lookupAddress('0x6fC21092DA55B392b045eD78F4732bff3C580e2c').then(function(name) {
        console.log(name);
        // 'registrar.firefly.eth'
    });

## Contract Execution

These are relatively low-level calls. The Contracts API should usually be used instead.

prototype . call ( transaction )

  Send the read-only (constant) transaction to a single Ethereum node and return a Promise with the result (as a hex string) of executing it. (See Transaction Requests)

  This is free, since it does not change any state on the blockchain.

prototype . estimateGas ( transaction )

  Send a transaction to a single Ethereum node and return a Promise with the estimated amount of gas required (as a BigNumber) to send it. (See Transaction Requests)

  This is free, but only an estimate. Providing too little gas will result in a transaction being rejected (while still consuming all provided gas).

prototype . sendTransaction ( signedTransaction )

  Send the signedTransaction to the entire Ethereum network and returns a Promise with the transaction hash.

  This will consume gas from the account that signed the transaction.

### Examples

Call (Constant) Functions

    var ethers = require('ethers');
    var provider = ethers.providers.getDefaultProvider();

    // setup a transaction to call the CryptoKitties.symbol() function
    // CryptoKitties contract address
    var address = "0x06012c8cf97BEaD5deAe237070F9587f8E7A266d";
    // first 8 nibbles of the hash of symbol()
    var data = ethers.utils.id('symbol()').substring(0,10);
    var transaction = {
        to: address,
        data: data
    }

    provider.call(transaction).then(function(result) {
        console.log(result);
        // '0x000000000000000000000000000000000000000000000000000000000000002'+
        // '00000000000000000000000000000000000000000000000000000000000000002'+
        // '434b000000000000000000000000000000000000000000000000000000000000'
    });

sendTransaction

    var ethers = require('ethers');
    var privateKey = '0x0123456789012345678901234567890123456789012345678901234567890123';
    var wallet = new ethers.Wallet(privateKey);
    wallet.provider = ethers.providers.getDefaultProvider('ropsten');

    var transaction = {
        to: "0x88a5C2d9919e46F883EB62F7b8Dd9d0CC45bc290",
        value: ethers.utils.parseEther("0.1")
    };

    var estimateGasPromise = wallet.estimateGas(transaction);

    estimateGasPromise.then(function(gasEstimate) {
        console.log(gasEstimate.toString());
        transaction.gasLimit = gasEstimate;

        // Send the transaction
        var sendTransactionPromise = wallet.sendTransaction(transaction);

        sendTransactionPromise.then(function(transactionHash) {
           console.log(transactionHash);
        });
    });

## Contract State

prototype . getCode ( addressOrName )
  Returns a Promise with the bytecode (as a hex string) at addressOrName.
prototype . getStorageAt ( addressOrName , position [ , blockTag ] )

  Returns a Promise with the value (as a hex string) at addressOrName in position at blockTag. (See Block Tags)

  default: blockTag= “latest”

prototype . getLogs ( filter )
  Returns a Promise with an array (possibly empty) of the logs that match the filter. (See Filters)

### Examples

getCode

    var ethers = require('ethers');
    var provider = ethers.providers.getDefaultProvider();

    var contractAddress = '0x6fC21092DA55B392b045eD78F4732bff3C580e2c';
    var contractEnsName = 'registrar.firefly.eth';
    var codePromise = provider.getCode(contractEnsName);
    codePromise.then(function(result){
       console.log('getCode by ENS name:');
       console.log(result);
    });

    var codeByAddressPromise = provider.getCode(contractAddress);
    codeByAddressPromise.then(function(result){
       console.log('getCode by contract address:');
       console.log(result);
    });

getStorageAt

    var ethers = require('ethers');
    var provider = ethers.providers.getDefaultProvider();

    var contractEnsName = 'registrar.firefly.eth';
    var storagePromise = provider.getStorageAt(contractEnsName, 0);
    storagePromise.then(function(result){
       console.log(result);
    });

getLogs

    var ethers = require('ethers');
    var provider = ethers.providers.getDefaultProvider();

    var cryptoKittiesContractAddress = '0x06012c8cf97BEaD5deAe237070F9587f8E7A266d';
    var topic = '0x241ea03ca20251805084d27d4440371c34a0b85ff108f6bb5611248f73818b80';
    var filter = {
       fromBlock: 5044502,
       address: cryptoKittiesContractAddress,
       topics: [ topic ]
    }
    var filterPromise = provider.getLogs(filter);
    filterPromise.then(function(result){
       console.log(result);
    });

## Events

These methods allow management of callbacks on certain events on the blockchain and contracts. They are largely based on the EventEmitter API.

prototype . on ( eventType , callback )
  Register a callback for any future eventType; see below for callback parameters
prototype . once ( eventType , callback)
  Register a callback for the next (and only next) eventType; see below for callback parameters
prototype . removeListener ( eventType , callback )
  Unregister the callback for eventType; if the same callback is registered more than once, only the first registered instance is removed
prototype . removeAllListeners ( eventType )
  Unregister all callbacks for eventType
prototype . listenerCount ( [ eventType ] )
  Return the number of callbacks registered for eventType, or if ommitted, the total number of callbacks registered
prototype . resetEventsBlock ( blockNumber )
  Begin scanning for events from blockNumber. By default, events begin at the block number that the provider began polling at.

### Event Types

“block”

  Whenever a new block is mined

  `callback( blockNumber )`

any address

  When the balance of the corresponding address changes

  `callback( balance )`

any transaction hash

  When the corresponding transaction is mined; also see Waiting for Transactions

  `callback( transaction )`

an array of topics

  When any of the topics are triggered in a block’s logs; when using the Contract API, this is automatically handled;

  `callback( log )`

### Waiting for Transactions

prototype . waitForTransaction ( transactionHash [ , timeout ] )
  Return a Promise which returns the transaction once transactionHash is mined, with an optional timeout (in milliseconds)

### Examples

    // Get notified on every new block
    provider.on('block', function(blockNumber) {
        console.log('New Block: ' + blockNumber);
    });

    // Get notified on account balance change
    provider.on('0x46Fa84b9355dB0708b6A57cd6ac222950478Be1d', function(balance) {
        console.log('New Balance: ' + balance);
    });

    // Get notified when a transaction is mined
    provider.once(transactionHash, function(transaction) {
        console.log('Transaction Minded: ' + transaction.hash);
        console.log(transaction);
    );

    // OR equivalently the waitForTransaction() returns a Promise

    provider.waitForTransaction(transactionHash).then(function(transaction) {
        console.log('Transaction Mined: ' + transaction.hash);
        console.log(transaction);
    });

    // Get notified when a contract event is logged
    var eventTopic = '0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef';
    provider.on([ eventTopic ], function(log) {
        console.log('Event Log');
        console.log(log);
    });

## Objects

There are several common objects and types that are commonly used as input parameters or return types for various provider calls.

### Block Tag

A block tag is used to uniquely identify a block’s position in the blockchain:

a Number or hex string:
  Each block has a block number (eg. `42` or `"0x2a`.
“latest”:
  The most recently mined block.
“pending”:
  The block that is currently being mined.

### Block Responses

    {
        parentHash: "0x3d8182d27303d92a2c9efd294a36dac878e1a9f7cb0964fa0f789fa96b5d0667",
        hash: "0x7f20ef60e9f91896b7ebb0962a18b8defb5e9074e62e1b6cde992648fe78794b",
        number: 3346463,

        difficulty: 183765779077962,
        timestamp: 1489440489,
        nonce: "0x17060cb000d2c714",
        extraData: "0x65746865726d696e65202d20555331",

        gasLimit: utils.bigNumberify("3993225"),
        gasUsed: utils.bigNuberify("3254236"),

        miner: "0xEA674fdDe714fd979de3EdF0F56AA9716B898ec8",
        transactions: [
            "0x125d2b846de85c4c74eafb6f1b49fdb2326e22400ae223d96a8a0b26ccb2a513",
            "0x948d6e8f6f8a4d30c0bd527becbe24d15b1aba796f9a9a09a758b622145fd963",
            ... [ 49 more transaction hashes ] ...
            "0xbd141969b164ed70388f95d780864210e045e7db83e71f171ab851b2fba6b730"
        ]
    }

### Transaction Requests

Any property which accepts a number may also be specified as a BigNumber or hex string.

    // Example:
    {
        // Required unless deploying a contract (in which case omit)
        to: addressOrName,  // the target address or ENS name

        // These are optional/meaningless for call and estimateGas
        nonce: 0,           // the transaction nonce
        gasLimit: 0,        // the maximum gas this transaction may spend
        gasPrice: 0,        // the price (in wei) per unit of gas

        // These are always optional (but for call, data is usually specified)
        data: "0x",         // extra data for the transaction, or input for call
        value: 0,           // the amount (in wei) this transaction is sending
        chainId: 3          // the network ID; usually added by a signer
    }

### Transaction Response

    // Example:
    {
        // Only available for mined transactions
        blockHash: "0x7f20ef60e9f91896b7ebb0962a18b8defb5e9074e62e1b6cde992648fe78794b",
        blockNumber: 3346463,
        transactionIndex: 51,

        // Exactly one of these will be present (send vs. deploy contract)
        creates: null,
        to: "0xc149Be1bcDFa69a94384b46A1F91350E5f81c1AB",

        // The transaction hash
        hash: "0xf517872f3c466c2e1520e35ad943d833fdca5a6739cfea9e686c4c1b3ab1022e",

        // See above (Transaction Requests) for these explained
        data: "0x",
        from: "0xEA674fdDe714fd979de3EdF0F56AA9716B898ec8",
        gasLimit: utils.bigNumberify("90000"),
        gasPrice: utils.bigNumberify("21488430592"),
        nonce: 0,
        value: utils.parseEther(1.0017071732629267),

        // The network ID (or chain ID); 0 indicates replay-attack vulnerable
        // (eg. 1 = Homestead mainnet, 3 = Ropsten testnet)
        networkId: 1,

        // The signature of the transaction
        r: "0x5b13ef45ce3faf69d1f40f9d15b0070cc9e2c92f3df79ad46d5b3226d7f3d1e8",
        s: "0x535236e497c59e3fba93b78e124305c7c9b20db0f8531b015066725e4bb31de6",
        v: 37,

        // The raw transaction
        raw: "0xf87083154262850500cf6e0083015f9094c149be1bcdfa69a94384b46a1f913" +
               "50e5f81c1ab880de6c75de74c236c8025a05b13ef45ce3faf69d1f40f9d15b0" +
               "070cc9e2c92f3df79ad46d5b3226d7f3d1e8a0535236e497c59e3fba93b78e1" +
               "24305c7c9b20db0f8531b015066725e4bb31de6"
    }

### Transaction Receipts

    // Example
    {
        transactionHash: "0x7dec07531aae8178e9d0b0abbd317ac3bb6e8e0fd37c2733b4e0d382ba34c5d2",

        // The block this transaction was mined into
        blockHash: "0xca1d4d9c4ac0b903a64cf3ae3be55cc31f25f81bf29933dd23c13e51c3711840",
        blockNumber: 3346629,

        // The index into this block of the transaction
        transactionIndex: 1,

        // The address of the contract (if one was created)
        contractAddress: null,

        // Gas
        cumulativeGasUsed: utils.bigNumberify("42000"),
        gasUsed: utils.bigNumberify("21000"),

        // Logs
        log: [ ],
        logsBloom: "0x00" ... [ 256 bytes of 0 ] ... "00",

        // Post-Byzantium hard-fork
        byzantium: false

        ////////////
        // Pre-byzantium blocks will have a state root:
        root: "0x8a27e1f7d3e92ae1a01db5cce3e4718e04954a34e9b17c1942011a5f3a942bf4",

        ////////////
        // Post-byzantium blocks will have a status (0 indicated failure during execution)
        // status: 1
    }

### Filters

Filtering on topics supports a somewhat complicated specification, however, for the vast majority of filters, a single topic is usually sufficient (see the example below).

The EtherscanProvider only supports a single topic.

    // Example
    {
        // Optional; The range of blocks to limit querying (See: Block Tags above)
        fromBlock: "latest",
        toBlock: "latest",

        // Optional; An address (or ENS name) to filter by
        address: addressOrName,

        // Optional; A (possibly nested) list of topics
        topics: [ topic1 ]
    }

## Provider Specific Extra API Calls

### Etherscan

prototype . getEtherPrice ( )
  Returns a Promise with the price of ether in USD.
prototype . getHistory ( addressOrName [ , startBlock [ , endBlock ] ] )
  Returns a Promise with an array of Transaction Responses for each transaction to or from addressOrName between startBlock and endBlock (inclusive).

Examples

    var provider = new ethers.providers.EtherscanProvider();

    // Getting the current Ethereum price
    provider.getEtherPrice().then(function(price) {
        console.log("Ether price in USD: " + price);
    });

    // Getting the transaction history of an address
    var address = '0xb2682160c482eB985EC9F3e364eEc0a904C44C23';
    var startBlock = 3135808;
    var endBlock = 5091477;
    provider.getHistory(address, startBlock, endBlock).then(function(history) {
        console.log(history);
        // [
        //   {
        //     hash: '0x327632ccb6d7bb47b455383e936b2f14e6dc50dbefdc214870b446603b468675',
        //     blockHash: '0x0415f0d2741de45fb748166c7dc2aad9b3ff66bcf7d0a127f42a71d3e286c36d',
        //     blockNumber: 3135808,
        //     transactionIndex: 1,
        //     from: '0xb2682160c482eB985EC9F3e364eEc0a904C44C23',
        //     gasPrice: ethers.utils.bigNumberify('0x4a817c800'),
        //     gasLimit: ethers.utils.bigNumberify('0x493e0'),
        //     to: '0xAe572713CfE65cd7033774170F029B7219Ee7f70',
        //     value: ethers.utils.bigNumberify('0xd2f13f7789f0000'),
        //     nonce: 25,
        //     data: '0x',
        //     creates: null,
        //     networkId: 0
        //   },
        //   {
        //     hash: '0x7c10f2e7125a1fa5e37b54f5fac5465e8d594f89ff97916806ca56a5744812d9',
        //     ...
        //   }
        // ]
    });

### Web3Provider

prototype . listAccounts ( )
  Returns a Promise with a list of all accounts the node connected to this Web3 controls.
prototype . getSigner( [ address ] )
  Returns a Signer that uses an account on the node the Web3 object is connected to. If no address is specified, the first account on the node is used.

Examples

    web3Provider.listAccounts().then(function(accounts) {
        var signer = web3Provider.getSigner(accounts[1]);
        console.log(signer);
    });