NodeJS: creating a hash and return the value of a function

Question

I have a list of tags that I need to extract. the list is called list.

I'm trying to find all 'og:*' meta that correspond to the list and are available in a fetched html. Then I need to return a hash to the user in JSON that contains these meta tags. But the process method return undefined rather than the hash.

var http = require('http');
var url = require('url');
var request = require('request');
var jsdom = require("jsdom");
var fs = require('fs');
var cssom = require('cssom');

var list = ['title', 'description']; //here the og-tags I need to extract
var meta = {};

function process(url) {
  request(url, function (error, response, body) {
    if (!error && response.statusCode == 200) {  
      jsdom.env({
        html: body,
        scripts: [
          'http://code.jquery.com/jquery-1.5.min.js'
        ],
        done: function(errors, window) {
          var $ = window.$;

          $('meta[property^="og:"]').each(function() {
            for (var element in list) {
              if ($(this).attr('property') == 'og:' + list[element]) {
                meta[list[element]] = $(this).attr('content');

                // this works well, if I do console.log(meta), I get the hash correctly filled.
              }
            }
          });
        }
      });
    }
  });

  return meta; // this is where the probleme is. This return undefined.
}


http.createServer(function (request, response) {
  request.setEncoding('utf8');
  response.writeHead(200, {'Content-Type': 'text/plain'});

  process(url.parse(request.url, true).query['content'], function(result) {
    console.log(result); // prints no result
  });

  response.end();
}).listen(8124);

console.log('Server running at http://0.0.0.0:8124');

Try not to use process as the name of that function, it's a NodeJS variable through which you can access information related to the node process itself. API Link — Gautham Badhrinathan
– Gautham Badhrinathan, Commented Aug 20, 2012 at 20:39

JohnnyHK · Accepted Answer · 2012-08-20 20:45:10Z

1

Because request is asynchronous, you need to make process asynchronous as well. That means having process accept a callback parameter that it will call once meta is available. As it is now, process is returning meta before the request callback populates it.

function process(url, callback) {
  request(url, function (error, response, body) {
    if (!error && response.statusCode == 200) {  
      jsdom.env({
        html: body,
        scripts: [
          'http://code.jquery.com/jquery-1.5.min.js'
        ],
        done: function(errors, window) {
          var $ = window.$;

          $('meta[property^="og:"]').each(function() {
            for (var element in list) {
              if ($(this).attr('property') == 'og:' + list[element]) {
                meta[list[element]] = $(this).attr('content');
                callback(null, meta);
              }
            }
          });
        }
      });
    } else {
      callback(error);
    }
  });
}


http.createServer(function (request, response) {
  request.setEncoding('utf8');
  response.writeHead(200, {'Content-Type': 'text/plain'});

  process(url.parse(request.url, true).query['content'], function(error, result) {
    console.log(result); // prints no result
  });

  response.end();
}).listen(8124);

edited Aug 20, 2012 at 20:45

answered Aug 20, 2012 at 20:26

JohnnyHK

313k70 gold badges632 silver badges479 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Beetroot-Beetroot Over a year ago

@JohnyHK, a subsidiary question if I may: does request() return a promise, like $.ajax() in client-side jQuery?

JohnnyHK Over a year ago

@Beetroot-Beetroot Not to my knowledge, no. See the docs here: github.com/mikeal/request

Collectives™ on Stack Overflow

NodeJS: creating a hash and return the value of a function

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related