Basic example of Lambda function that accepts both GraphQL & API gateway requests

index.js

exports.handler = function (event, context) { //eslint-disable-line
  const taxTable = {
    NY: 8.49, CA: 8.56, OK: 8.92, FL: 7.05,
    IL: 8.74, PA: 6.34, WA: 9.17, TX: 8.19
  }

  let price
  let taxRate
  if (event.arguments) {
    // graphql request
    price = event.arguments.price
    taxRate = taxTable[event.arguments.location]
  } else {
    price = event.price
    taxRate = taxTable[event.location]
  }

  let calculatedTax = (taxRate / 100) * price
  calculatedTax = Math.round( ( calculatedTax + Number.EPSILON ) * 100 ) / 100

  const finalPrice = (calculatedTax + price).toFixed(2)

  const response = {
    calculatedTax,
    finalPrice
  }

  context.done(null, response);
};