web3.js

web3.js is a Javascript library for building on EVM-compatible networks.

It allows developers to interact with smart contracts, send transactions, and retrieve data from the network.

Installation

This guide assumes you have the latest version of Node.js installed.

To install web3, run the following command:

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npm install web3

Connecting to Flow

To use web3 in your project, start by imporing the module and initializing your Web3 provider the desired Flow RPC endpoint.

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const { Web3 } = require('web3')

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const web3 = new Web3('https://mainnet.nodes.fff')

info

Currently, only Previewnet is available. More networks are coming soon, see here for more info.

Interacting With Smart Contracts

web3.js allows developers to interact with smart contracts via the web3.eth.Contract API.

A Contract object must be instantiated as follows:

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const abi = [

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... // ABI of deployed contract

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]

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const contractAddress

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const contract =

info

To deploy your own contract on EVM, see the documentation using Hardhat or Remix.

Methods on the smart contract can now be called in the following ways.

Querying state

We can query data from the contract by using the call function on one of the contract's methods. This will not mutate the state and will not send a transaction.

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const result = contract.methods.someGetterFunction().call()

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console.log(result)

Mutating state

If you wish to mutate the contract's state, you may do so with the send function on one of the contract's methods. This will possibly mutate the state and will send a transaction.

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const argument = 1

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const sender = "0x1234" // replace with the address this transaction will be sent from

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const result = await contract.methods.someSetterFunction(argument).call({

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from: sender

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})

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console.log(result)

The transaction will be signed automatically by web3js, as long as the sender's address is registered as an account in the provider.

For more information about using smart contracts in web3.js, see the official documentation.