algorithmicCoder
algorithmicCoder

Reputation: 6789

How do run multiple asynchronous functions in this node code?

I'm pulling text from N urls. First I get the N urls in linksOnPage and then i run a doOnPage function to get the text from each url. When i run code only 1 of the N urls gets processed through the function. I assume it's because the processing function is running asynchronously. How do I stack these up in a queue and run them all/ whats a better way to do this?

Here's the main JS code:

var nodeio, linksOnPage, lyricsFromLink, db;

nodeio = require('node.io');
db = require('./db');
db.loadDB();

var loadSong =  function(artist, title, lyrics){
    console.log("loadSong being called");
    var newSongObj = {};
    newSongObj['artist'] = artist;  
    newSongObj['title'] = title;
    newSongObj['lyrics'] = lyrics;
    //store the lyrics in a mongo table
    var newSong = new db.Song(newSongObj);
    newSong.save(function(err) {
        if(err){
            throw err;
        } else{
            console.log("saved with no errors!");
        }
    });
};
// generic utility for getting links on a page and running a function on each one
exports.linksOnPage = function(pageObj, linkSelector, doOnPage, contentSelector) {
    nodeio.scrape(function(){
        this.getHtml(pageObj.pageUrl, function(err, $) {
            var links = [];
            var i = 0;
            $(linkSelector).each(function(link) {
                var fullLink = pageObj.rootUrl + link.attribs.href
                links.push(fullLink);
                //run a function on each link
                console.log('getting lyrics for song: ', i);
                doOnPage(pageObj.artist, fullLink, contentSelector);
                i = i+1;
            });
            //this.emit(links);
        });
    });
}

// get the lyrics for a specific song 
exports.lyricsFromLink = function(artist, pageUrl, lyricsSelector) {
    nodeio.scrape(function(){
        this.getHtml(pageUrl, function(err, $) {
            var lyrics = "";
            console.log('before each statement');
            $(lyricsSelector).each(function(lyricParagraph) {
                lyrics = lyrics + " " + lyricParagraph.text;
            });
            console.log('after each statement');
            loadSong(artist, pageUrl, lyrics);
            this.emit(lyrics)
        });
    });
}

Upvotes: 0

Views: 81

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