CODEWITHSUNDEEP
javascriptfunctionrecursion
Jake Stanger
Jake Stanger

Reputation: 449

Waiting for Recursive Function To Complete

I have a recursive Javascript function which gets the links from one Wikipedia page, follows them, and then gets all of those links (repeating a specified number of times).

It calls itself an unknown number of times to construct an object of a known depth. When it completes, I want to output the object. Currently the object immediately outputs, and is empty, meaning the function obviously isn't waiting for all the recursive calls to complete.

As you can see, I have attempted to use callbacks, but I assume incorrectly. What am I doing wrong, how should I be doing it? I'm going to presume there's a few other things wrong I haven't spotted too; I'm relatively new to Javascript.

$(document).ready(function ()
{
  pageLinks[START_PAGE] = {};
  //Get initial pages
  links = getLinks(START_PAGE, 0, printLinks));
});

function printLinks()
{
  console.log(links);
}

function getLinks(currentPage, level, callback)
{
  visitedPages.push(currentPage)
  var pageLinks = {}
  var data = $.getJSON(URL_BEGIN + currentPage + URL_END, function(data)
  {
    var pages = data.query.pages;
    for(var page in pages)
    {
      pageContentObj = pages[page].revisions[0];
      for(var key in pageContentObj) if(pageContentObj[key].length > 100)
      {
        var pageContent = pageContentObj[key];
        //Get links
        hyperlinks = getFromBetween.get(pageContent,"[[","]]");
        for(var link in hyperlinks)
        {
          link = hyperlinks[link].split("|")[0]; //Remove friendly name
          link = link.replaceAll(" ", "%20");

          //Add to pagelist object
          prefix = link.split(":")[0];
          if(prefix != "Category" && prefix != "File" && prefix != "wikipedia")
            if(level < ITERATIONS && !visitedPages.includes(arguments, link))
            {
              console.log(level + ": " + link)
              pageLinks[link] = getLinks(link, level+1, callback); //===Recursive call===
            }
        }
      }
    }
  });
  if(level == 0 && callback) callback();
  return pageLinks;
}

Any help is appreciated, thanks in advance.

**EDIT: ** Link: https://github.com/JakeStanger/Wikipedia-Mapper/blob/master/init.js#L53

Upvotes: 1

Views: 1931

Answers (1)

Jonas Wilms
Jonas Wilms

Reputation: 138267

The recursive call needs to be like this:

var counter = 0;
//the big for loop
counter++;
getLinks(link, level + 1, function(res) {
    for (var key in res) { //with an array it would be concat...
        pageLinks[key] = res[key];
    }
    counter--;
    if (counter == 0 && callback) callback(pageLinks); //callback if all callbacks called
});

Also remove this weird code:

if(level == 0 && callback) callback();

No you can do:

getLinks(START_PAGE, 0, console.log);

Upvotes: 2

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