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Alchemy Web3

Web3 client extended with Alchemy and browser provider integration.

Introduction

Alchemy Web3 provides website authors with a drop-in replacement for the web3.js Ethereum API client. It produces a client matching that of web3.js, but brings multiple advantages to make use of Alchemy API:

  • Uses Alchemy or an injected provider as needed. Most requests will be sent through Alchemy, but requests involving signing and sending transactions are sent via a browser provider like Metamask or Trust Wallet if the user has it installed, or via a custom provider specified in options.

  • Easy access to Alchemy's higher level API. The client exposes methods to call Alchemy's exclusive features.

  • Automatically retries on rate limited requests. If Alchemy returns a 429 response (rate limited), automatically retry after a short delay. This behavior is configurable.

  • Robust WebSocket subscriptions which don't miss events if the WebSocket needs to be reconnected.

Alchemy Web3 is designed to require minimal configuration so you can start using it in your app right away.

Installation

With a package manager

With Yarn:

yarn add @alch/alchemy-web3

Or with NPM:

npm install @alch/alchemy-web3

With a CDN in the browser

Alternatively, add one of the following script tags to your page:

<!-- Minified -->
<script src="https://cdn.jsdelivr.net/npm/@alch/alchemy-web3@latest/dist/alchemyWeb3.min.js"></script>
<!-- Unminified -->
<script src="https://cdn.jsdelivr.net/npm/@alch/alchemy-web3@latest/dist/alchemyWeb3.js"></script>

When using this option, you can create Alchemy-Web3 instances using the global variable AlchemyWeb3.createAlchemyWeb3.

Usage

Basic Usage

You will need an Alchemy account to access the Alchemy API. If you don't have one yet, sign up here.

Create the client by importing the function createAlchemyWeb3 and then passing it your Alchemy app's URL and optionally a configuration object.

import { createAlchemyWeb3 } from "@alch/alchemy-web3";

// Using HTTPS
const web3 = createAlchemyWeb3(
  "https://eth-mainnet.alchemyapi.io/v2/<api-key>",
);

or

// Using WebSockets
const web3 = createAlchemyWeb3(
  "wss://eth-mainnet.ws.alchemyapi.io/ws/<api-key>",
);

You can use any of the methods described in the web3.js API and they will send requests to Alchemy:

// Many web3.js methods return promises.
web3.eth.getBlock("latest").then((block) => {
  /* … */
});

web3.eth
  .estimateGas({
    from: "0xge61df…",
    to: "0x087a5c…",
    data: "0xa9059c…",
    gasPrice: "0xa994f8…",
  })
  .then((gasAmount) => {
    /* … */
  });

With a Browser Provider

If the user has a provider in their browser available at window.ethereum, then any methods which involve user accounts or signing will automatically use it. This provider might be injected by Metamask, Trust Wallet or other browsers or browser extensions if the user has them installed. For example, the following will use a provider from the user's browser:

web3.eth.getAccounts().then((accounts) => {
  web3.eth.sendTransaction({
    from: accounts[0],
    to: "0x6A823E…",
    value: "1000000000000000000",
  });
});

Note on using Metamask

As just discussed, Metamask will automatically be used for accounts and signing if it is installed. However, for this to work you must first request permission from the user to access their accounts in Metamask. This is a security restriction required by Metamask: details can be found here.

To enable the use of Metamask, you must call ethereum.enable(). An example of doing so is as follows:

if (window.ethereum) {
  ethereum
    .enable()
    .then((accounts) => {
      // Metamask is ready to go!
    })
    .catch((reason) => {
      // Handle error. Likely the user rejected the login.
    });
} else {
  // The user doesn't have Metamask installed.
}

Note that doing so will display a Metamask dialog to the user if they have not already seen it and accepted, so you may choose to wait to enable Metamask until the user is about to perform an action which requires it. This is also why Alchemy Web3 will not automatically enable Metamask on page load.

With a custom provider

You may also choose to bring your own provider for writes rather than relying on one being present in the browser environment. To do so, use the writeProvider option when creating your client:

const web3 = createAlchemyWeb3(ALCHEMY_URL, { writeProvider: provider });

Your provider should expose at least one of sendAsync() or send(), as specified in EIP 1193.

You may swap out the custom provider at any time by calling the setWriteProvider() method:

web3.setWriteProvider(provider);

You may also disable the write provider entirely by passing a value of null.

Automatic Retries

If Alchemy Web3 encounters a rate limited response, it will automatically retry the request after a short delay. This behavior can be configured by passing the following options when creating your client. To disable retries, set maxRetries to 0.

maxRetries

The number of times the client will attempt to resend a rate limited request before giving up. Default: 3.

retryInterval

The minimum time waited between consecutive retries, in milliseconds. Default: 1000.

retryJitter

A random amount of time is added to the retry delay to help avoid additional rate errors caused by too many concurrent connections, chosen as a number of milliseconds between 0 and this value. Default: 250.

Sturdier WebSockets

Alchemy Web3 brings multiple improvements to ensure correct WebSocket behavior in cases of temporary network failure or dropped connections. As with any network connection, you should not assume that a WebSocket will remain open forever without interruption, but correctly handling dropped connections and reconnection by hand can be challenging to get right. Alchemy Web3 automatically adds handling for these failures with no configuration necessary.

If you use your WebSocket URL when initializing, then when you create subscriptions using web3.eth.subscribe(), Alchemy Web3 will bring the following advantages over standard Web3 subscriptions:

  • Unlike standard Web3, you will not permanently miss events which arrive while the backing WebSocket is temporarily down. Instead, you will receive these events as soon as the connection is reopened. Note that if the connection is down for more than 120 blocks (approximately 20 minutes), you may still miss some events that were not part of the most recent 120 blocks.

  • Compared to standard Web3, lowered rate of failure when sending requests over the WebSocket while the connection is down. Alchemy Web3 will attempt to send the requests once the connection is reopened. Note that it is still possible, with a lower likelihood, for outgoing requests to be lost, so you should still have error handling as with any network request.

Alchemy's Transfers API

The produced client also grants easy access to Alchemy's transfer API.

web3.alchemy.getAssetTransfers({fromBlock, toBlock, fromAddress, toAddress, contractAddresses, excludeZeroValue, maxCount, category, pageKey})

Returns an array of asset transfers based on the specified parameters.

Parameters:

An object with the following fields:

  • fromBlock: Optional inclusive from hex string block (default latest)
  • toBlock: Optional inclusive to hex string block (default latest)
  • order: Optional string that specifies the ordering of the results by block number. Must be one of ["asc", "desc"] (default "asc")
  • fromAddress: Optional from hex string address (default wildcard)
  • toAddress: Optional to hex string address (default wildcard) NOTE: fromAddress is ANDed with toAddress
  • contractAddresses: Optional array of hex string contract addresses for "token" transfers (default wildcard) NOTE: contractAddresses are ORed together
  • excludeZeroValue: Optional boolean to exclude transfers with zero value (default true)
  • maxCount: Optional number to restrict payload size (default and max of 1000)
  • category: Optional array of categories (defaults to the following categories: ["external", "internal", "token"])
  • pageKey: Optional uuid pageKey to retrieve the next payload

Returns:

An object with the following fields:

  • pageKey: Uuid for next page of results (undefined for the last page of results).
  • transfers: An array of objects with the following fields sorted in ascending order by block number
    • category: "external", "internal", "token", "erc20", "erc721", "erc1155" - label for the transfer
    • blockNum: The block where the transfer occurred (hex string).
    • from: From address of transfer (hex string).
    • to: To address of transfer (hex string). null if contract creation.
    • value: Converted asset transfer value as a number (raw value divided by contract decimal). null if erc721 transfer or contract decimal not available.
    • erc721TokenId: Raw erc721 token id (hex string). null if not an erc721 transfer
    • erc1155Metadata: A list of objects containing the erc1155 tokenId (hex string) and value (hex string). null if not an erc1155 transfer
    • asset: "ETH" or the token's symbol. null if not defined in the contract and not available from other sources.
    • hash: Transaction hash (hex string).
    • rawContract: Object of raw values:
      • value: Raw transfer value (hex string). null if erc721 or erc1155 transfer
      • address: Contract address (hex string). null if "external" or "internal"
      • decimal: Contract decimal (hex string). null if not defined in the contract and not available from other sources.

Alchemy's Enhanced API

The produced client also grants easy access to Alchemy's enhanced API.

web3.alchemy.getTokenAllowance({contract, owner, spender})

Returns token balances for a specific address given a list of contracts.

Parameters:

An object with the following fields:

  • contract: The address of the token contract.
  • owner: The address of the token owner.
  • spender: The address of the token spender.

Returns:

The allowance amount, as a string representing a base-10 number.

web3.alchemy.getTokenBalances(address, contractAddresses)

Returns token balances for a specific address given a list of contracts.

Parameters:

  1. address: The address for which token balances will be checked.
  2. contractAddresses: An optional array of contract addresses. Not specifying this will return all token balances.

Returns:

An object with the following fields:

  • address: The address for which token balances were checked.
  • tokenBalances: An array of token balance objects. Each object contains:
    • contractAddress: The address of the contract.
    • tokenBalance: The balance of the contract, as a string representing a base-10 number.
    • error: An error string. One of this or tokenBalance will be null.

web3.alchemy.getTokenMetadata(address)

Returns metadata (name, symbol, decimals, logo) for a given token contract address.

Parameters:

address: The address of the token contract.

Returns:

An object with the following fields:

  • name: The token's name. null if not defined in the contract and not available from other sources.
  • symbol: The token's symbol. null if not defined in the contract and not available from other sources.
  • decimals: The token's decimals. null if not defined in the contract and not available from other sources.
  • logo: URL of the token's logo image. null if not available.

web3.alchemy.getNfts({owner, pageKey, contractAddresses})

Parameters:

An object with the following fields:

  • owner: The address that you want to fetch NFTs for.
  • pageKey: (Optional) A key to fetch the next page of results.
  • contractAddresses: (Optional) An array of contract addresses to filter the owner's results to.
  • withMetadata: (Optional) If false, the returned NFTs will omit metadata. Defaults to true.

Returns:

When metadata is included, the returned object has the following fields:

  • ownedNfts: An array of NFT objects that the address owns. Each NFT object has the following structure.
    • contract:
      • address: The address of the contract or collection that the NFT belongs to.
    • id:
      • tokenId: Raw token id.
      • tokenMetadata:
        • tokenType: The type of token being sent as part of the request (Can be one of ["erc721" | "erc1155"]).
    • title: The title of the NFT, or an empty string if no title is available.
    • description: The descriptions of the NFT, or an empty string if no description is available.
    • tokenUri: (Optional)
      • raw: Uri representing the location of the NFT's original metadata blob. This is a backup for you to parse when the metadata field is not automatically populated.
      • gateway: Public gateway uri for the raw uri.
    • media: (Optional) An array of objects with the following structure.
      • uri: A tokenUri as described above.
    • metadata: (Optional)
      • image: (Optional) A uri string that should be usable in an tag.
      • attributes: (Optional) An array of attributes from the NFT metadata. Each attribute is a dictionary with unknown keys and values, as they depend directly on the contract.
    • timeLastUpdated: ISO timestamp of the last cache refresh for the information returned in the metadata field.
  • pageKey: (Optional) A key to fetch the next page of results, if applicable.
  • totalCount: The total number of NFTs in the result set.

If metadata is omitted, an object with the following fields is returned:

  • ownedNfts: An array of NFT objects that the address owns. Each NFT object has the following structure.
    • contract:
      • address: The address of the contract or collection that the NFT belongs to.
    • id:
      • tokenId: Raw token id.
      • tokenMetadata:
        • tokenType: The type of token being sent as part of the request (Can be one of ["erc721" | "erc1155"]).
  • pageKey: (Optional) A key to fetch the next page of results, if applicable.
  • totalCount: The total number of NFTs in the result set.

web3.alchemy.getNftMetadata({contractAddress, tokenId, tokenType})

Parameters:

An object with the following fields:

  • contract: The address of the token contract.
  • tokenId: Raw token id (hex string).
  • tokenType: (Optional) The type of token being sent as part of the request (Can be one of ["erc721" | "erc1155"]).

Returns:

An object with the following fields:

  • contract:
    • address: The hex string of the contract addresses for "token" transfers.
  • id:
    • tokenId: Raw token id.
    • tokenMetadata:
      • tokenType: The type of token being sent as part of the request (Can be one of ["erc721" | "erc1155"]).
  • title: Name of NFT.
  • description: A brief description of the NFT taken from the contract metadata.
  • tokenUri: (Optional)
    • raw: Uri representing the location of the NFT's original metadata blob. This is a backup for you to parse when the metadata field is not automatically populated.
    • gateway: Public gateway uri for the raw uri.
  • media: (Optional) An array of objects with the following structure.
    • uri: A tokenUri as described above.
  • metadata: (Optional)
    • image: (Optional) A uri string that should be usable in an tag.
    • attributes: (Optional) An array of attributes from the NFT metadata. Each attribute is a dictionary with unknown keys and values, as they depend directly on the contract.
  • timeLastUpdated: ISO timestamp of the last cache refresh for the information returned in the metadata field.

web3.alchemy.getTransactionReceipts({blockNumber | blockHash})

Fetches all transaction receipts for a block number or a block hash.

Parameters:

  • blockNumber - (hex) The block number to get transaction receipts for
  • blockHash - The block hash to get transaction receipts for

Note that either blockNumber or blockHash can be set.

Returns:

  • {receipts: TransactionReceipt[]} | null - An array of transaction receipts, or null if the block number or hash is not found.

The returned object is a list of transaction receipts for each transaction in this block. See eth_getTransactionReceipt for the payload of an individual transaction receipt.

web3.eth.subscribe("alchemy_fullPendingTransactions")

Subscribes to pending transactions, similar to the standard Web3 call web3.eth.subscribe("pendingTransactions"), but differs in that it emits full transaction information rather than just transaction hashes.

Note that the argument passed to this function is permitted to be either of "alchemy_fullPendingTransactions" or "alchemy_newFullPendingTransactions", which have the same effect. The latter is the string used in raw eth_subscribe JSON-RPC calls, while the former is consistent with the existing Web3.js subscription APIs (for example, web3.eth.subscribe("pendingTransactions") corresponds to the raw JSON-RPC call of type newPendingTransactions). While this is unfortunately confusing, supporting both strings attempts to balance consistency and convenience.

web3.eth.subscribe("alchemy_filteredFullPendingTransactions", options)

Like an alchemy_fullPendingTransactions subscription, but also allows passing an options argument containing an address field to filter the returned transactions to those from or to the specified address. The options argument is as described in the documentation here.

Similar to the previous point, note that the argument passed to this function may be either of "alchemy_filteredFullPendingTransactions" or "alchemy_filteredNewPendingTransactions".


Copyright © 2019 Alchemy Insights Inc.

EIP 1559

web3.eth.getFeeHistory(blockRange, startingBlock, percentiles[])

Fetches the fee history for the given block range as per the eth spec.

Parameters

  • blockRange: The number of blocks for which to fetch historical fees. Can be an integer or a hex string.
  • startingBlock: The block to start the search. The result will look backwards from here. Can be a hex string or a predefined block string e.g. "latest".
  • percentiles: (Optional) An array of numbers that define which percentiles of reward values you want to see for each block.

Returns

An object with the following fields:

  • oldestBlock: The oldest block in the range that the fee history is being returned for.
  • baseFeePerGas: An array of base fees for each block in the range that was looked up. These are the same values that would be returned on a block for the eth_getBlockByNumber method.
  • gasUsedRatio: An array of the ratio of gas used to gas limit for each block.
  • reward: Only returned if a percentiles parameter was provided. Each block will have an array corresponding to the percentiles provided. Each element of the nested array will have the tip provided to miners for the percentile given. So if you provide [50, 90] as the percentiles then each block will have a 50th percentile reward and a 90th percentile reward.

Example

Method call

web3.eth.getFeeHistory(4, "latest", [25, 50, 75]).then(console.log);

Logged response

{
  oldestBlock: 12930639,
  reward: [
    [ '0x649534e00', '0x66720b300', '0x826299e00' ],
    [ '0x649534e00', '0x684ee1800', '0x7ea8ed400' ],
    [ '0x5ea8dd480', '0x60db88400', '0x684ee1800' ],
    [ '0x59682f000', '0x5d21dba00', '0x5d21dba00' ]
  ],
  baseFeePerGas: [ '0x0', '0x0', '0x0', '0x0', '0x0' ],
  gasUsedRatio: [ 0.9992898398856537, 0.9999566454373825, 0.9999516, 0.9999378 ]
}

web3.eth.getMaxPriorityFeePerGas()

Returns a quick estimate for maxPriorityFeePerGas in EIP 1559 transactions. Rather than using feeHistory and making a calculation yourself you can just use this method to get a quick estimate. Note: this is a geth-only method, but Alchemy handles that for you behind the scenes.

Parameters

None!

Returns

A hex, which is the maxPriorityFeePerGas suggestion. You can plug this directly into your transaction field.

Example

Method call

web3.eth.getMaxPriorityFeePerGas().then(console.log);

Logged response

0x560de0700