No result from callback function in Node.js

Question

I want to execute callback function

function recurring_end() {

var sql= "SELECT `bookmarks`.`id`,`bookmarks`.`bookmark_url` as url FROM bookmarks LIMIT 0, 10";

connection.query(sql, function(err,bookmarks) {
     for(var i = 0; i< bookmarks.length; i++){
        (function(i) {

                parseArticle(i,function(err,result){
                    console.log("Result is "+JSON.stringify(result));
                        NewParseArtilce(result,function() {
                                console.log("New Parse Artilce is " +i);
                    });

                });
         })(i);
     }
});
}
function NewParseArtilce(i,callback){
    console.log("New Article Number is is "+i);

}
function parseArticle(i,callback) {
    console.log("Parse Article Number is " +i);

return i;
};

This is my code. I am executing parseArticle Function first and then i want to pass result into newParseArticle But i am not getting any result in parseArtilce.

Any idea, why it is causing problem

Thanks

majidarif · Accepted Answer · 2014-11-03 04:52:18Z

1

Because your parseArticle is synchronous. It should be:

function parseArticle(i, callback) {
  console.log("Parse Article Number is " +i);
  callback(null, i); // executes the callback, null is err and i is result
}

Also your last console.log won't get executed. You should do this:

function NewParseArtilce(i,callback){
  console.log("New Article Number is is "+i);
  callback(); // executes the callback
}

edited Nov 3, 2014 at 4:52

answered Nov 3, 2014 at 4:44

majidarif

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2 Comments

Hitu Bansal Over a year ago

what is null. How you do you this is synchronous or asynchronous please

majidarif Over a year ago

@HituBansal Simply put, when using callback = asynchronous. When using return = synchronous. Understand Callbacks.

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