Node.js <Class> is not a constructor

Question

I'm getting "HttpHandlers is not a constructor" error when trying to instantiate that class using "new".

Class being instantiated (../lib/restifyHandlers/HttpHandlers):

var config = require('config');
module.exports.config = config;

var util = require('util');
var _ = require('underscore');
var EventEmitter = require("events").EventEmitter;

var HttpHandlers  = function(eventHandlers) {
    var _self = this;
    this.name = "HttpHandlers";
    if (!(this instanceof HttpHandlers)) {
        return new HttpHandlers(eventHandlers);
    }
}

util.inherits(HttpHandlers, EventEmitter);

HttpHandlers.prototype.extractHttpHandlersRequest = function(req, res, next) {
    var _self = this;
    req.locals = {};
    res.locals = {};

}
module.exports.HttpHandlers = HttpHandlers;

Code making the call:

var HttpHandlers = require('../lib/restifyHandlers/HttpHandlers');
var obj = new HttpHandlers(oneRouteConfig.eventHandlers);

Stacktrace:

2016-09-10T23:44:41.571-04:00 - [31merror[39m: Sun, 11 Sep 2016 03:44:41 GMT Worker #master: exiting from error:  TypeError: HttpHandlers is not a constructor 
TypeError: HttpHandlers is not a constructor
    at setupRestifyRoute (/usr/apps/das/src/myrepo/nodejs/myapp/lib/router.js:78:14)
    at Router.setup_routes (/usr/apps/das/src/myrepo/nodejs/myapp/lib/router.js:40:3)
    at /usr/apps/das/src/myrepo/nodejs/myapp/bin/server.js:222:14
    at initialize (/usr/apps/das/src/myrepo/nodejs/myapp/bin/server.js:38:9)
    at setup_server (/usr/apps/das/src/myrepo/nodejs/myapp/bin/server.js:107:4)
    at /usr/apps/das/src/myrepo/nodejs/myapp/bin/server.js:275:4
    at /usr/apps/das/src/myrepo/nodejs/myapp/node_modules/temp/lib/temp.js:231:7
    at FSReqWrap.oncomplete (fs.js:123:15)

Answer 1

When you assigned this:

exports.HttpHandlers = HttpHandlers;

You would need to match that with this:

var HttpHandlers = require('../lib/restifyHandlers/HttpHandlers').HttpHandlers;

---

You are assigning a property of your module to be .HttpHandlers, not assigning the whole module so if you want that property, you have to reference the property. If you want it to work the other way, you could change to this:

exports = HttpHandlers;

And, then your require() could work the way you are doing it like this:

var HttpHandlers = require('../lib/restifyHandlers/HttpHandlers');

Answer 2

I got this error when calling new ClassName(); and it was caused in the ClassName class by missing off the "module." from module.exports = ClassName

Just in case someone else is as daft as me...

Answer 3

I got this error because I had some cyclic import. So the class was undefined..

If it can help someone else !