iso-url/src/relative.js

Isomorphic/Universal WHATWG URL API with some support legacy node URL API

'use strict'

const { URLWithLegacySupport, format } = require('./url')

/**
 * @param {string | undefined} url
 * @param {any} [location]
 * @param {any} [protocolMap]
 * @param {any} [defaultProtocol]
 */
module.exports = (url, location = {}, protocolMap = {}, defaultProtocol) => {
  let protocol = location.protocol
    ? location.protocol.replace(':', '')
    : 'http'

  // Check protocol map
  protocol = (protocolMap[protocol] || defaultProtocol || protocol) + ':'
  let urlParsed

  try {
    urlParsed = new URLWithLegacySupport(url)
  } catch (err) {
    urlParsed = {}
  }

  const base = Object.assign({}, location, {
    protocol: protocol || urlParsed.protocol,
    host: location.host || urlParsed.host
  })

  return new URLWithLegacySupport(url, format(base)).toString()
}