Using Ethers.js

This guide will help you install the V3 SDK and ethers.js to query state data from Ethereum. While this tutorial doesn't use the V3 SDK - it will set us up to use it after we get the on-chain data we need.

First Steps

For our first step, we're going to use ethers.js return immutable variables from a Uniswap V3 pool contract, and assign them to an interface in our script that can be repeatedly referenced without continually reading state data directly from the EVM.

We'll need to make a new directory called example

mkdir examplecd example

then we'll make a new project using node

npm init

npm i typescript --savenpm i ts-node --savenpm i @uniswap/v3-sdk --savenpm i @uniswap/sdk-core i --savenpm i ethers  --save

Depending on your machine configuration, you may also need this:

npm install -D tslib @types/node

Importing Ethers and the V3 SDK

We'll need to import ethers, and set up our environment variables so we can query chain data. For this example, we're using an infura endpoint. If you don't have access to an infura endpoint, you can setup a free account here.

import { ethers } from "ethers";import { Pool } from "@uniswap/v3-sdk";import { Address } from "cluster";
const provider = new ethers.providers.JsonRpcProvider("<YOUR-ENDPOINT-HERE>");

The first thing we'll need to do is to tell ethers where to look for our chain data. To do this we'll create a local variable with the contract address of the V3 pool we're trying to query.

const poolAddress = "0x8ad599c3A0ff1De082011EFDDc58f1908eb6e6D8";

Now we'll need the interface for the functions of the pool contract that we'll be calling

const poolImmutablesAbi = [  "function factory() external view returns (address)",  "function token0() external view returns (address)",  "function token1() external view returns (address)",  "function fee() external view returns (uint24)",  "function tickSpacing() external view returns (int24)",  "function maxLiquidityPerTick() external view returns (uint128)",];

Using ethers.js "Contract"

Once that is setup, we create a new instance of a "Contract" using ethers.js. This isn't a smart contract itself, but rather a local model of one that helps us move data around off chain.

const poolContract = new ethers.Contract(  poolAddress,  poolImmutablesAbi,  provider);

Now we'll create an interface with all the data we're going to return, each assigned to its appropriate type

interface Immutables {  factory: Address;  token0: Address;  token1: Address;  fee: number;  tickSpacing: number;  maxLiquidityPerTick: number;}

Returning Chain Data

now we're ready to query the EVM using ethers.js, and assign the returned values to the variables inside of our Immutables interface.

async function getPoolImmutables() {  const PoolImmutables: Immutables = {    factory: await poolContract.factory(),    token0: await poolContract.token0(),    token1: await poolContract.token1(),    fee: await poolContract.fee(),    tickSpacing: await poolContract.tickSpacing(),    maxLiquidityPerTick: await poolContract.maxLiquidityPerTick(),  };  return PoolImmutables;}

finally, we can call our function, and print out the returned data in our console:

Calling Our Function

getPoolImmutables().then((result) => {  console.log(result);});

to call out function, we'll navigate to our project directory within our console, and use this command

npx ts-node example.ts

If everything worked correctly, you should see something like this:

➜  example npx ts-node example.ts{  factory: '0x1F98431c8aD98523631AE4a59f267346ea31F984',  token0: '0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48',  token1: '0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2',  fee: 3000,  tickSpacing: 60,  maxLiquidityPerTick: BigNumber {    _hex: '0x023746e6a58dcb13d4af821b93f062',    _isBigNumber: true  }}

The Final Script

import { ethers } from "ethers";import { Pool } from "@uniswap/v3-sdk";import { Address } from "cluster";
const provider = new ethers.providers.JsonRpcProvider("<YOUR_ENDPOINT_HERE>");
const poolAddress = "0x8ad599c3A0ff1De082011EFDDc58f1908eb6e6D8";
const poolImmutablesAbi = [  "function factory() external view returns (address)",  "function token0() external view returns (address)",  "function token1() external view returns (address)",  "function fee() external view returns (uint24)",  "function tickSpacing() external view returns (int24)",  "function maxLiquidityPerTick() external view returns (uint128)",];
const poolContract = new ethers.Contract(  poolAddress,  poolImmutablesAbi,  provider);
interface Immutables {  factory: Address;  token0: Address;  token1: Address;  fee: number;  tickSpacing: number;  maxLiquidityPerTick: number;}
async function getPoolImmutables() {  const PoolImmutables: Immutables = {    factory: await poolContract.factory(),    token0: await poolContract.token0(),    token1: await poolContract.token1(),    fee: await poolContract.fee(),    tickSpacing: await poolContract.tickSpacing(),    maxLiquidityPerTick: await poolContract.maxLiquidityPerTick(),  };  return PoolImmutables;}
getPoolImmutables().then((result) => {  console.log(result);});