@pulsadev/defi-router

DEX swap router — optimal path finding, multi-hop routing, price quotes, multi-DEX comparison, calldata generation. Zero dependencies, pure RPC.

Find the best swap route across multiple DEXes and paths. Build transaction calldata ready to submit. No SDK required.

Features

• Optimal path finding — direct and multi-hop routes via intermediate tokens
• Multi-DEX comparison — compare quotes across Uniswap, SushiSwap, PancakeSwap, etc.
• Price quotes — getAmountsOut / getAmountsIn with accurate fee calculation
• Swap calldata generation — build ready-to-submit transaction data
• Price impact calculation — know your slippage before swapping
• 7 chains / 10+ DEXes — Ethereum, BSC, Polygon, Arbitrum, Optimism, Base, Avalanche
• Auto chain detection — pass an RPC URL, DEX config loads automatically
• Built-in intermediate tokens — WETH, USDC, USDT, DAI per chain for multi-hop routing
• Uniswap V2 math — pure JS constant product AMM calculations
• Zero dependencies — ~12 KB bundled, ESM + CJS, pure TypeScript

Install

npm install @pulsadev/defi-router

Quick Start

Get a swap quote

import { DefiRouter } from '@pulsadev/defi-router'

const router = new DefiRouter({ rpcUrl: 'https://ethereum-rpc.publicnode.com' })

const quote = await router.getQuote(
  '0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2', // WETH
  '0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48', // USDC
  1000000000000000000n, // 1 ETH
)

console.log(`Best output: ${quote.bestAmountOut} USDC`)
console.log(`Via: ${quote.bestRoute.dex.name}`)
console.log(`Path: ${quote.bestRoute.path.join(' → ')}`)
console.log(`Price impact: ${quote.bestRoute.priceImpact}%`)
console.log(`Routes found: ${quote.routes.length}`)

Compare across DEXes

const best = await router.findBestDex(WETH, USDC, 1000000000000000000n)
console.log(`Best DEX: ${best.dex.name} — ${best.amountOut} out`)

Build swap calldata

const calldata = router.buildSwapCalldata({
  tokenIn: WETH,
  tokenOut: USDC,
  amountIn: 1000000000000000000n,
  slippageBps: 50, // 0.5%
  recipient: '0xYourAddress...',
}, quote.bestRoute)

// Ready to submit
console.log(`To: ${calldata.to}`)
console.log(`Data: ${calldata.data}`)
console.log(`Value: ${calldata.value}`)

Use on any chain

// Auto-detects chain and loads DEX config
const bscRouter = new DefiRouter({ rpcUrl: 'https://bsc-dataseed.binance.org' })
const polygonRouter = new DefiRouter({ rpcUrl: 'https://polygon-bor-rpc.publicnode.com', chainId: 137 })

API

new DefiRouter(options)

| Option | Type | Description | |--------|------|-------------| | rpcUrl | string | RPC endpoint URL | | chainId | number | Chain ID (auto-detected if omitted) | | dexes | DexConfig[] | Custom DEX configs (auto-loaded if omitted) | | intermediateTokens | Address[] | Tokens for multi-hop (auto-loaded if omitted) |

Methods

| Method | Description | |--------|-------------| | getQuote(tokenIn, tokenOut, amountIn) | Find all routes and return best quote | | getAmountsOut(dex, path, amountIn) | Calculate output amounts along a path | | findBestDex(tokenIn, tokenOut, amountIn) | Compare single-hop across all DEXes | | buildSwapCalldata(params, route) | Build swapExactTokensForTokens calldata | | buildSwapExactETHCalldata(params, route) | Build swapExactETHForTokens calldata | | pairExists(dex, tokenA, tokenB) | Check if a pair exists | | getDexes() | Get configured DEX list | | getIntermediateTokens() | Get intermediate token list |

Standalone utilities

| Function | Description | |----------|-------------| | getAmountOut(amountIn, reserveIn, reserveOut, feeBps) | Uniswap V2 output calculation | | getAmountIn(amountOut, reserveIn, reserveOut, feeBps) | Uniswap V2 input calculation | | getPriceImpact(amountIn, reserveIn) | Calculate price impact % | | getPairAddress(rpcUrl, factory, tokenA, tokenB) | Query pair address from factory | | getPairReserves(rpcUrl, pairAddress) | Get pair reserves | | sortTokens(tokenA, tokenB) | Sort token pair |

Supported DEXes

| Chain | DEXes | |-------|-------| | Ethereum (1) | Uniswap V2, SushiSwap | | BSC (56) | PancakeSwap V2 | | Polygon (137) | QuickSwap, SushiSwap | | Arbitrum (42161) | SushiSwap | | Optimism (10) | Velodrome | | Base (8453) | Uniswap V2 | | Avalanche (43114) | TraderJoe |

License

MIT © Yuto Nakamura