Recursive function in node.js using q library

Question

I need to prepare JSON by fetching the data from MYSQL. I have data in MYSQl in tree structure. I am trying to make recursive function to prepare JSON to meet the requirement but getting errors, I have following two files

main.js

/* jshint node: true */
"use strict";

var db = require('./helpers/db');
var list_worker = require('./workers/list');
var Q = require("q");

module.exports = function (app) {
/**
 * return the profiles list
 */
app.get('/api/lists/get_list_tree_by_user/:user_id', function (req, res) {

    list_worker.fetch_list_tree(req.params.user_id, 0).done(function (out) {
        console.log(out);
        res.send(out);
    });
});
};

list.js

/* jshint node: true */
"use strict";

var db = require('../helpers/db');
var Q = require("q");
var output = {
    data: []
};

var fetch_list_tree = function (user_id, list_id) {

// prepare query to fetch lists assosiated with a user.
var query = "SELECT b.`id`, b.`name` FROM `lists_users` a JOIN `lists` b ON(a.`list_id` = b.`id`) WHERE a.`user_id` = " + user_id + " AND a.`user_role` = 'owner' AND b.`parent_id` = " + list_id + " AND b.`deleted` = 'N';";

return db.query(query).then(function (result) {

    if (result.length > 0) {
        var lists = result.map(function (list, index) {

            output.data[index] = {
                label: list.name,
                data: {
                    id: list.id
                }
            };

            return fetch_list_tree(user_id, list.id).then(function (leaf_childs) {
                output.data[index].children = [];
                output.data[index].children.push(leaf_childs);
                return leaf_childs;
            });
        });

        return Q.all(lists).then(function (data) {
            return output;
        }, function (err) {
            throw err;
        });
    } else {
        return [];
    }
}, function (err) {
    throw err;
});
};

module.exports = {
    fetch_list_tree: fetch_list_tree
};

data in database I am having is item 1 item 1.1 item 1.1.1 item 2

Output I want { "label": "item 1", "data": { "id": "1" }, "children": [{ "label": "item 1.1", "data": { "id": "2" }, "children": [{ "label": "item 1.1.1", "data": { "id": "3" }, "children": [] }] }] }

I am getting the following error

TypeError: Converting circular structure to JSON

score 0 · Answer 1 · answered Jul 22 '16 at 18:04

0

Try change this.fetch_list_tree to exports.fetch_list_tree.

this != module.exports on line 28 => undefined

answered Jul 22 '16 at 18:04

Aikon Mogwai

4,954
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I am getting the error after updating this.fetch_list_tree to exports.fetch_list_tree TypeError: exports.fetch_list_tree is not a function – Jatin Seth Jul 23 '16 at 01:01
I did some R&D and got the problem, I was not able to call the function, I have made some changes in list.js but not getting desired out, I updated the current error too. I am not able to handle `output` as it should be. – Jatin Seth Jul 23 '16 at 06:23
`Converting circular structure to JSON` means that some node of result reference by itself. Try `JSON.stringify(result, ['label', 'data', 'children'])`. – Aikon Mogwai Jul 23 '16 at 06:47

Recursive function in node.js using q library

1 Answers1