serverless-offline/src/utils/parseMultiValueQueryStringParameters.js

Emulate AWS λ and API Gateway locally when developing your Serverless project

import { BASE_URL_PLACEHOLDER } from "../config/index.js"

const { fromEntries } = Object

// https://aws.amazon.com/blogs/compute/support-for-multi-value-parameters-in-amazon-api-gateway/
// [ [ 'petType', 'dog' ], [ 'petType', 'fish' ] ]
// => { petType: [ 'dog', 'fish' ] },
export default function parseMultiValueQueryStringParameters(url) {
  // dummy placeholder url for the WHATWG URL constructor
  // https://github.com/nodejs/node/issues/12682
  const { searchParams } = new URL(url, BASE_URL_PLACEHOLDER)

  if (Array.from(searchParams).length === 0) {
    return null
  }

  const map = new Map()

  // eslint-disable-next-line no-restricted-syntax
  for (const [key, value] of searchParams) {
    const item = map.get(key)

    if (item) {
      item.push(value)
    } else {
      map.set(key, [value])
    }
  }

  return fromEntries(map)
}