00-callback-hell.md

From https://www.geeksforgeeks.org/what-is-callback-hell-in-node-js/

app.get("/details", function (req, res) {
    var name = req.query.name;
    console.log(name);

    Scopus.find({ name: name },
        { '_id': 0, 'authorId': 1 },
        function (err, result) {
            if (err) { }
            else {
                var searchResult = result[0]["authorId"];
                console.log(searchResult);
                var options = {
                    url: "https://api.elsevier.com/content/author/author_id/"
                        + searchResult + "?apiKey",
                    headers: { 'Accept': 'application/json' }
                };
                request(options, function (error, response, body) {
                    if (error) {

                        // Print the error if one occurred
                        console.error('error in Authors :', error);

                        // Print the response status code if a response was received
                        console.log('statusCode:', response && response.statusCode);
                        res.send("error")
                    }
                    else if (!error) {
                        var jsonObj = JSON.parse(body);
                        if (jsonObj['author-retrieval-response'] == undefined) {
                            res.send("No details");
                        }
                        else {
                            var reqData = jsonObj['author-retrieval-response'][0];
                            var authprofile = reqData["author-profile"]
                            var names = authprofile["preferred-name"]["indexed-name"]
                            console.log(names);
                            var citation = reqData["coredata"]["citation-count"];
                            var query = { authorId: searchResult };

                            Scopus.findOneAndUpdate(query, {
                                name: names,
                                citationCount: citation
                            }, function (err, doc, res) {
                                if (err) {
                                    console.log("error");
                                }
                                else {
                                    console.log("success");
                                }
                            })
                            res.render("details", { data: reqData });
                        }
                    }
                });
            }
        })
});