Fetch API wrapper

path.js

const existy = value => value !== null && value !== undefined

export function resolve (host, relative, params) {
  const path = `${host}/${relative}`
  if (params) {
    return `${path}?${toQueryParams(params)}`
  }
  return path
}

export function toQueryParams (params) {
  return params ? Object.keys(params).filter(key => existy(params[key])).map(key => `${encodeURIComponent(key)}=${encodeURIComponent(params[key])}`).join('&') : ''
}

request.js

import { resolve } from '../utils/path'

const TIMEOUT_MSEC = 10000

const timeout = (msec, promise) => {
  return new Promise((resolve, reject) => {
    const tid = setTimeout(() => {
      reject(new Error(`Request has been timed out (${msec} msec)`))
    }, msec)
    promise.then(
      response => {
        clearTimeout(tid)
        resolve(response)
      },
      error => {
        clearTimeout(tid)
        reject(error)
      }
    )
  })
}

const wrap = fetch => {
  return new Promise((resolve, reject) => {
    fetch.then(response => {
      if (response.ok) {
        resolve(response.json())
      } else {
        reject(response)
      }
    })
  })
}

export function request (method, host, relative, params) {
  const path = resolve(host, relative, method === 'GET' ? params : null)
  const options = {
    method,
    cache: 'no-cache',
    mode: 'cors',
    credentials: 'include'
  }
  switch (method) {
    case 'POST':
    case 'PUT':
    case 'PATCH':
    case 'DELETE':
      options.headers = new Headers({ 'Content-Type': 'application/json' })
      options.body = params ? JSON.stringify(params) : '{}'
      break
    default:
      break
  }
  return timeout(TIMEOUT_MSEC, wrap(fetch(path, options)))
}