Explain what a provider is...

Accounts Methods

provider.getBalance( address [ , blockTag = latest ] ) Promise< BigNumber >

Returns the balance of address as of the blockTag block height.

provider.getCode( address [ , blockTag = latest ] ) Promise< string< DataHexString > >

Returns the contract code of address as of the blockTag block height. If there is no contract currently deployed, the result is 0x.

provider.getStorageAt( addr , pos [ , blockTag = latest ] ) Promise< string< DataHexString > >

Returns the Bytes32 value of the position pos at address addr, as of the blockTag.

provider.getTransactionCount( address [ , blockTag = latest ] ) Promise< number >

Returns the number of transactions address has ever sent, as of blockTag. This value is required to be the nonce for the next transaction from address sent to the network.

Account Examples
// Get the balance for an account... provider.getBalance("ricmoo.firefly.eth"); // { Promise: { BigNumber: "1492974808274631213" } } // Get the code for a contract... provider.getCode("registrar.firefly.eth"); // { Promise: '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} // Get the storage value at position 0... provider.getStorageAt("registrar.firefly.eth", 0) // { Promise: '0x000000000000000000000000314159265dd8dbb310642f98f50c066173c1259b' } // Get transaction count of an account... provider.getTransactionCount("ricmoo.firefly.eth"); // { Promise: 679 }

Blocks Methods

provider.getBlock( block ) Promise< Block >

Get the block from the network, where the result.transactions is a list of transaction hashes.

provider.getBlockWithTransactions( block ) Promise< BlockWithTransactions >

Get the block from the network, where the result.transactions is an Array of TransactionResponse objects.

Block Examples
provider.getBlock(100004) // { Promise: { // difficulty: 3849295379889, // extraData: '0x476574682f76312e302e312d39383130306634372f6c696e75782f676f312e34', // gasLimit: { BigNumber: "3141592" }, // gasUsed: { BigNumber: "21000" }, // hash: '0xf93283571ae16dcecbe1816adc126954a739350cd1523a1559eabeae155fbb63', // miner: '0x909755D480A27911cB7EeeB5edB918fae50883c0', // nonce: '0x1a455280001cc3f8', // number: 100004, // parentHash: '0x73d88d376f6b4d232d70dc950d9515fad3b5aa241937e362fdbfd74d1c901781', // timestamp: 1439799168, // transactions: [ // '0x6f12399cc2cb42bed5b267899b08a847552e8c42a64f5eb128c1bcbd1974fb0c' // ] // } } provider.getBlockWithTransactions(100004) // { Promise: { // difficulty: 3849295379889, // extraData: '0x476574682f76312e302e312d39383130306634372f6c696e75782f676f312e34', // gasLimit: { BigNumber: "3141592" }, // gasUsed: { BigNumber: "21000" }, // hash: '0xf93283571ae16dcecbe1816adc126954a739350cd1523a1559eabeae155fbb63', // miner: '0x909755D480A27911cB7EeeB5edB918fae50883c0', // nonce: '0x1a455280001cc3f8', // number: 100004, // parentHash: '0x73d88d376f6b4d232d70dc950d9515fad3b5aa241937e362fdbfd74d1c901781', // timestamp: 1439799168, // transactions: [ // { // blockHash: '0xf93283571ae16dcecbe1816adc126954a739350cd1523a1559eabeae155fbb63', // blockNumber: 100004, // chainId: 0, // confirmations: 10719007, // creates: null, // data: '0x', // from: '0xcf00A85f3826941e7A25BFcF9Aac575d40410852', // gasLimit: { BigNumber: "90000" }, // gasPrice: { BigNumber: "54588778004" }, // hash: '0x6f12399cc2cb42bed5b267899b08a847552e8c42a64f5eb128c1bcbd1974fb0c', // nonce: 25, // r: '0xb23adc880d3735e4389698dddc953fb02f1fa9b57e84d3510a2a4b3597ac2486', // s: '0x4e856f95c4e2828933246fb4765a5bfd2ca5959840643bef0e80b4e3a243d064', // to: '0xD9666150A9dA92d9108198a4072970805a8B3428', // transactionIndex: 0, // v: 27, // value: { BigNumber: "5000000000000000000" } // } // ] // } }

Ethereum Naming Service (ENS) Methods

The Ethereum Naming Service (ENS) allows a short and easy-to-remember ENS Name to be attached to any set of keys and values.

One of the most common uses for this is to use a simple name to refer to an Ethereum Address.

In the ethers API, nearly anywhere that accepts an address, an ENS name may be used instead, which can simplify code and make reading and debugging much simpler.

The provider offers some basic operations to help resolve and work with ENS names.

provider.lookupAddress( address ) Promise< string >

Performs a reverse lookup of the address in ENS using the Reverse Registrar. If the name does not exist, or the forward lookup does not match, null is returned.

provider.resolveName( name ) Promise< string< Address > >

Looks up the address of name. If the name is not owned, or does not have a Resolver configured, or the Resolver does not have an address configured, null is returned.

ENS Examples
// Reverse lookup of an ENS by address... provider.lookupAddress("0x6fC21092DA55B392b045eD78F4732bff3C580e2c"); // { Promise: 'registrar.firefly.eth' } // Lookup an address of an ENS name... provider.resolveName("ricmoo.firefly.eth"); // { Promise: '0x8ba1f109551bD432803012645Ac136ddd64DBA72' }

Logs Methods

provider.getLogs( filter ) Promise< Array< Log > >

Returns the Array of Log matching the filter.

Keep in mind that many backends will discard old events, and that requests which are too broad may get dropped as they require too many resources to execute the query.

Network Status Methods

provider.getNetwork( ) Promise< Network >

Returns the Network this Provider is connected to.

provider.getBlockNumber( ) Promise< number >

Returns the block number (or height) of the most recently mined block.

provider.getGasPrice( ) Promise< BigNumber >

Returns a best guess of the Gas Price to use in a transaction.

Network Status Examples
// The network information provider.getNetwork() // { // chainId: 1, // ensAddress: '0x00000000000C2E074eC69A0dFb2997BA6C7d2e1e', // name: 'homestead' // } // The current block number provider.getBlockNumber() // { Promise: 10819010 } // Get the current suggested gas price (in wei)... gasPrice = await provider.getGasPrice() // { BigNumber: "69000000000" } // ...often this gas price is easier to understand or // display to the user in gwei (giga-wei, or 1e9 wei) utils.formatUnits(gasPrice, "gwei") // '69.0'

Transactions Methods transaction [ , blockTag = latest ] ) Promise< string< DataHexString > >

Returns the result of executing the transaction, using call. A call does not require any ether, but cannot change any state. This is useful for calling gettings on Contracts.

provider.estimateGas( transaction ) Promise< BigNumber >

Returns an estimate of the amount of gas that would be required to submit transaction to the network.

An estimate may not be accurate since there could be another transaction on the network that was not accounted for, but after being mined affected relevant state.

provider.sendTransaction( transaction ) Promise< TransactionResponse >

Submits transaction to the network to be mined. The transaction must be signed, and be valid (i.e. the nonce is correct and the account has sufficient balance to pay for the transaction).

provider.waitForTransaction( hash [ , confirms = 1 [ , timeout ] ] ) Promise< TxReceipt >

Returns a Promise which will not resolve until transactionHash is mined.

Event Emitter Methods

Explain events here...

provider.on( eventName , listener ) this

Add a listener to be triggered for each eventName.

provider.once( eventName , listener ) this

Add a listener to be triggered for only the next eventName, at which time it be removed.

provider.emit( eventName , ...args ) boolean

Notify all listeners of eventName, passing args to each listener. This is generally only used internally. eventName [ , listener ] ) this

Remove a listener for eventName. If no listener is provided, all listeners for eventName are removed.

provider.removeAllListeners( [ eventName ] ) this

Remove all the listeners for eventName. If no eventName is provided, all events are removed.

provider.listenerCount( [ eventName ] ) number

Returns the number of listeners for eventName. If no eventName is provided, the total number of listeners is returned.

provider.listeners( eventName ) Array< Listener >

Returns the list of Listeners for eventName.


Any of the following may be used as the eventName in the above methods.

Log Filter

A filter is an object, representing a contract log Filter, which has the optional properties address (the source contract) and topics (a topic-set to match).

If address is unspecified, the filter matches any contract address.

See events for more information on how to specify topic-sets.

Topic-Set Filter

The value of a Topic-Set Filter is a array of Topic-Sets.

This event is identical to a Log Filter with the address omitted (i.e. from any contract).

Transaction Filter

The value of a Transaction Filter is any transaction hash.

This event is emitted on every block that is part of a chain that includes the given mined transaction. It is much more common that the once method is used than the on method.

In addition to transaction and filter events, there are several named events.

Event NameArgumentsDescription 
"block"blockNumberemitted when a new block is mined 
"error"erroremitted on any error 
"pending"pendingTransactionemitted when a new transaction enters the memory pool; only certain providers offer this event and may require running your own node for reliable results 
"willPoll"pollIdemitted prior to a polling loop is about to begin; (very rarely used by most developers) 
"poll"pollId, blockNumberemitted during each poll cycle after `blockNumber` is updated (if changed) and before any other events (if any) are emitted during the poll loop; (very rarely used by most developers) 
"didPoll"pollIdemitted after all events from a polling loop are emitted; (very rarely used by most developers) 
"debug"provider dependenteach Provider may use this to emit useful debugging information and the format is up to the developer; (very rarely used by most developers) 
Named Provider Events 
Events Example
provider.on("block", (blockNumber) => { // Emitted on every block change }) provider.once(txHash, (transaction) => { // Emitted when the transaction has been mined }) // This filter could also be generated with the Contract or // Interface API. If address is not specified, any address // matches and if topics is not specified, any log matches filter = { address: "dai.tokens.ethers.eth", topics: ["Transfer(address,address,uint256)") ] } provider.on(filter, (log, event) => { // Emitted whenever a DAI token transfer occurs }) // Notice this is an array of topic-sets and is identical to // using a filter with no address (i.e. match any address) topicSets = ["Transfer(address,address,uint256)"), null, [ myAddress, myOtherAddress ] ] provider.on(topicSets, (log, event) => { // Emitted any token is sent TO either address }) provider.on("pending", (tx) => { // Emitted when any new pending transaction is noticed }); provider.on("error", (tx) => { // Emitted when any error occurs });

Inspection Methods

Provider.isProvider( object ) boolean

Returns true if and only if object is a Provider.