ajax interface

const createHeaders = ({
  json = true,
  ...rest
}) => {
  const headers = new Headers()
  if (json) {
    headers.append('Content-type', 'application/json')
  }
  Object.keys(rest).forEach(key => {
    headers.append(key, rest[key])
  })
  return headers
}

const WITH_BODY_METHODS = ['POST', 'PUT']

const ALLOWED_METHODS = ['GET', 'POST', 'PUT']

const createRequest = ({
  url,
  method,
  body,
  headersData: {
    json,
    ...rest
  }
}) => {
  if (typeof url !== 'string' || !url) {
    throw new Error('`url` is required')
  }
  if (typeof method !== 'string' || !method) {
    throw new Error('`method` is required')
  }
  if (ALLOWED_METHODS.indexOf(method.toUpperCase()) === -1) {
    throw new Error(`Method ${method} is not allowed`)
  }
  if (body && WITH_BODY_METHODS.indexOf(method) === -1) {
    throw new Error(`Only ${WITH_BODY_METHODS.join(', ')} can have \`body\` option`)
  }
  if (body === null) {
    throw new Error('`body` cannot be null')
  }
  if (typeof body === 'object') {
    body = JSON.parse(body)
  } else if (typeof body === 'string') {
    try {
      JSON.parse(body)
    } catch (error) {
      throw new Error('Cannot parse `body` param')
    }
  }
  const headers = createHeaders({ json, ...rest })
  const requestOptions = {
    credentials: 'include',
    method,
    headers
  }
  if (body) {
    requestOptions.body = body
  }
  const request = new Request(url, requestOptions)
  return request
}

const ajaxInterface = async (options) => {
  const request = createRequest(options)
  const response = await fetch(request)
  const data = await response.json()
}

class AjaxInterface {
  constructor() {
    
  }
}