Simple API to get a exchange rate from PancakeSwap V2 Router

getPrice.js

const express = require('express');
const { ethers } = require('ethers');
const app = express();
const port = 3000;

const provider = new ethers.providers.JsonRpcProvider('https://bsc-dataseed.binance.org/');

const contract = {
    factory: '0xcA143Ce32Fe78f1f7019d7d551a6402fC5350c73', // PancakeSwap V2 factory
    router: '0x10ED43C718714eb63d5aA57B78B54704E256024E', // PancakeSwap V2 router
};
const tokens = {
    BUSD: '0xe9e7cea3dedca5984780bafc599bd69add087d56',
    SCZ: '0x39f1014a88c8ec087cedf1bfc7064d24f507b894',
    DOP: '0x844fa82f1e54824655470970f7004dd90546bb28',
};

const router = new ethers.Contract(
    contract.router,
    ['function getAmountsOut(uint amountIn, address[] memory path) public view returns (uint[] memory amounts)'],
    provider
);

app.get('/getPrice', (req, res) => {

    let token = req.query.token;

    if(token.indexOf('0x') === -1){
        token = tokens[token.toUpperCase()];
    }
    
    if(token) {
        getPrice(token, tokens.BUSD).then(price => {
            res.json({
                success: true,
                BUSD: price
            });
        });

    }else{
        res.status(400).json({
            success: false,
            description: 'missing `token` parameter'
        });
    } 
});

app.listen(port, () => {
    console.log(`getPrice listening at http://localhost:${port}`)
});

async function getPrice(inputCurrency, outputCurrency){
    const amounts = await router.getAmountsOut(ethers.utils.parseUnits('1', 18), [inputCurrency, outputCurrency]);
    return amounts[1].toString()/1e18;
}