Precache images based on JSON response

preLoadInCache.js

'use strict'

var queue = require('async').queue
var cache = require("imgcache")
var _ = require('lodash')

// query the stories
// query content of eachStories
// then findURLInObject

// queue the query

let concurrency = 2

var q = async.queue(function(task, callback) {
    createOrUpdateCache(task.imageUrl, function(err, success){
        callback();
      })
    })
}, concurrency)

// assign a callback
q.drain = function() {
    console.log('all items have been processed');
}

var createOrUpdateCache = function(url, callback){
   ImgCache.isCached(url, function(path, success) {
    if (success) {
      console.log(`${url} is cached` )
      callback && callback(null, 'success')
    } else {
      // not there, need to cache the image
      ImgCache.cacheFile(url, function () {
        callback && callback(null, 'success')
        console.log(`${url} is now cached` )
      });
    }
}

var findURLInObject = function (JSONObject) {
  var result = []
  _.forOwn(JSONObject, function iterateObject(value, key) {
    if (_.isArrayLikeObject(value)) {
      _.each(value, function iterateArray(el, index) {
        result = _.concat(result, findURLInObject(el))
      })
    } else if (_.isPlainObject(value)) {
      result = _.concat(result, findURLInObject(value))
    } else if (_.isString(value) && value.indexOf('.jpg') > -1) {
      result.push(value)
    }
  })
  return result
}

let imageArray = findURLInObject(JSONRESPONSE)

startPreload = function(images){
  _.each(images, function(imageURL){
    q.push({imageURL: imageURL}, function(err) {
      if(err){
        console.error(`error while processing ${imageURL}`)
      } else {
        console.log(`finished processing ${imageURL}`)
      }
    })
  })
}