paraswap_node.js

const {ParaSwap} = require("paraswap");
const BN = require('bignumber.js');

const paraSwap = new ParaSwap(1, 'https://paraswap.io/api/v1');

async function getTokens(){
	return await paraSwap.getTokens();
}

async function getPrice(tokenFrom, tokenTo, srcAmount){
	return await paraSwap.getRate(tokenFrom, tokenTo, srcAmount);
}

async function buildTx(tokenFrom, tokenTo, srcAmount, minDestAmount, priceRoute, userAddress){
	return await paraSwap.buildTx(tokenFrom, tokenTo, srcAmount, minDestAmount, priceRoute, userAddress);
}

async function trade(from, to, _srcAmount, myAddress) {
	const tokens = await getTokens();

	const fromToken = tokens.find(token => token.symbol === from);

	const toToken = tokens.find(token => token.symbol === to);

	const srcAmount = new BN(_srcAmount).times(10**fromToken.decimals);

	const priceRoute = await getPrice(fromToken.address, toToken.address, srcAmount);

	const minDestAmount = new BN(priceRoute.amount).times(0.99).toFixed();

	const transaction = await buildTx(fromToken.address, toToken.address, srcAmount, minDestAmount, priceRoute, myAddress);

	return transaction;
}

trade("ETH", "DAI", 100, "0x80B1D1299602aedc567F4DC8db19076d186C6558")
	.then(transaction => console.log('transaction', transaction));