Nested async.eachSeries in waterfall executes in wrong order

Question

In second function in the async waterfall, the eachSeries callback (urlCallback) in my code executes after the waterfall callback (waterfallCallback), for reasons I cannot suss out.

   async.waterfall([
      function(callback) {
        request(website, function (error, response, html) {
            if (!error && response.statusCode == 200) {
              pageUrls = getPageUrls(html)
              callback(null, pageUrls)
            }
          })
      },
      function (pageUrls, waterfallCallback) {
          async.eachSeries(pageUrls, function (url, urlCallback) {
              console.log('SET ' + url)
              request(url, function (err, response, body) {
                  var $ = cheerio.load(body)
                  $('#div').children().each(function(){
                    console.log($(this).children("a").attr("href"));
                    itemUrl = $(this).children("a").attr("href")
                    itemUrls.push(itemUrl)
                  })
                  urlCallback(null,itemUrls)
              })
          },
          waterfallCallback(null, itemUrls))
      }
    ],
      function(err, results) {
        console.log("results: " + results)
    })

AFAIK, the async.eachSeries takes three arguments (array,functionToBeExecuteOnEachItem,callback) and execute them in that order. Somehow not here.

Answer 1

The parameters for async.eachSeries are function definitions. Something like waterfallCallback or function(err,result){}.

When you call waterfallCallback(null, itemUrls), that is not a function definition, that is running the function itself!

Changing to simply waterfallCallback should do the trick.

Update: Also, .eachSeries does not return the values as an array, its final callback is just function(err). Checkout .mapSeries link instead, which will return the resulting array in the final callback function(err,finalArray). (Be aware that each return of a .map will be an element in the array, so if you return an array, you'll get data structures like [ [], [], [] ])