generate URL of any RESTfull API Endpoint

api_config.js

/**
 * Components used to build the final URL
 * @type {Object}
 */
const urlComponents = {
  url: "http://myapi.mycompany.com/",
  prefix: "api",
  cart_uri: "/carts",
  cart_active_uri: "/active",
  cart_clean_uri: "/clean",
  suborder_uri: "/suborders",
  option_uri: "/options",
  auth_uri: "/auth",
  auth_login_uri: "/login",
  auth_signup_uri: "/signup",
  auth_recovery_uri: "/recovery",
  purchase_tunnel_uri: "/purchase_tunnel",
  purchase_tunnel_steps_uri: "/steps"
}

/**
 * Logic applied for a single Entity
 * @param  {string} entity [description]
 * @param  {string} action [description]
 * @param  {Object} params [description]
 * @return {string}        [description]
 */
let handleEntity = (entity, action, params) => {
  let url = "",
    entityParameter = params.hasOwnProperty(entity+'_id')? params[entity+'_id'] : false

  url += urlComponents[entity+'_uri']
  if (entityParameter) {
    url += '/'+entityParameter
  }
  //url += (action)? urlComponents[entity+'_'+action+'_'+'uri'] : ''
  if (action) url = url.concat(urlComponents[entity+'_'+action+'_'+'uri'])
  return url
}

/**
 * Deduce any RESTfull API endpoint from one or more Entity (and eventually an action)
 * then return the full URL
 * @param  {Array / string} entity
 * @param  {Object} [params={}]     optional
 * @param  {string} [action=null]   optional
 * @return {string}                 full URL
 */
//let generateURL = (entity, params = {}, action = null) => {
//let generateURL = (entity, action = null, params = {} ) => {
let generateURL = (entity, ...args) => {
  let url = urlComponents.url + urlComponents.prefix,
  [params = {}, action = null] = (typeof args[0] === 'string')? [args[1], args[0]] : [args[0], args[1]]

  // e.g. for this case: `/carts/{cart}/suborders/{suborder}/options`
  // is gotten from this call: `generateURL(["cart", "suborder", "option"], {
  // 'cart_id': xx, suborder_id: xxx} )`
  if (Array.isArray(entity)) {
    let lastEntity = entity[entity.length - 1],
      idx = lastEntity+'_'+action+'_'+'uri'
      lastAction = urlComponents.hasOwnProperty(idx)? urlComponents[idx] : false

    url += entity.reduce((acc, curr) => acc + handleEntity(curr, null, params), "")
    if (lastAction) url = url.concat(lastAction)
  }
  // simple case with one entity & an action (eventually)
  else if (urlComponents[entity+'_uri']) {
    url += handleEntity(entity, action, params)
  }
  return url
}