Unable to run a function synchronously in nodejs and express

Question

I have used wikipedia-js for this project. This is my code for summary.js file.

var wikipedia = require("wikipedia-js");
var something = "initial";
module.exports = {
    wikitext: function(topicname) {
        console.log("Inside wikitex funciton :" + topicname);
        var options = {
            query: topicname,
            format: "html",
            summaryOnly: false,
            lang: "en"
        };

        wikipedia.searchArticle(options, function(err, htmlWikiText) {
            console.log("Inside seararticlefunciton :");

            if (err) {
                console.log("An error occurred[query=%s, error=%s]", topicname, err);
                return;
            }
            console.log("Query successful[query=%s, html-formatted-wiki-text=%s]", topicname, htmlWikiText);
            something = htmlWikiText;
        });
        return something;
    },
};

This module I am using in /wiki/:topicname route. The corresponding code in index.js is like this.

router.get('/wiki/:topicname', function(req, res, next) {
    var topicname = req.params.topicname;
    console.log(topicname);
    var first = summary.wikitext(topicname);
    res.send("Hello "+first);
});

The problem is, everytime i visit a wiki/some-topic, the last return statement of summary.js executes before htmlWikiText is populated with content. So I always see hello initial on the browser page. Although after sometime it gets printed on terminal due to console.log statement.

So how should I resolve this issue?

Answer 1

I'm not going to try turning this code into synchronous. I'll just correct it to work as an asynchronous version.

You need to pass in callback to wikitext() and return the value in that callback. Here is the revised code of wikitext() and the route that calls it:

var wikipedia = require("wikipedia-js");
module.exports = {
    wikitext: function(topicname, callback) {
        console.log("Inside wikitex funciton :" + topicname);
        var options = {
            query: topicname,
            format: "html",
            summaryOnly: false,
            lang: "en"
        };

        wikipedia.searchArticle(options, function(err, htmlWikiText) {
            console.log("Inside seararticlefunciton :");
            if (err) {
                console.log("An error occurred[query=%s, error=%s]", topicname, err);
                return callback(err);
            }
            console.log("Query successful[query=%s, html-formatted-wiki-text=%s]", topicname, htmlWikiText);
            callback(null, htmlWikiText);
        });
    }
};


router.get('/wiki/:topicname', function(req, res, next) {
    var topicname = req.params.topicname;
    console.log(topicname);
    summary.wikitext(topicname, function(err, result) {
        if (err) {
            return res.send(err);
        }
        if (!result) {
            return res.send('No article found');
        }
        res.send("Hello "+result);

    });
});