CODEWITHSUNDEEP
javascriptnode.jsecmascript-6
James111
James111

Reputation: 15903

Node.js v6.2.0 class extends is not a function error?

So I'm trying to extend a class in node js and the compiler keeps returning the following error:

TypeError: Class extends value #<Object> is not a function or null

I checked that I was exporting the class correctly and I am, any ideas? I'll post my code below:

/handler/venue.js:

var VenueViews = require('../views/venue'); // If I remove this the error will dissapear (as expected)
class Venue {
  constructor(data) {
    this.setDataHere = data;
  }

  main () {
   var View = new VenueViews(); // This doesn't run
  }


}

module.exports = Venue;

/views/venue.js:

var Venue = require('../handlers/venue');
console.log  (Venue) // This returns {} ???

class VenueViews extends Venue {
  constructor() {
    super();
  }
}

module.exports = VenueViews;

I know that node supports these es6 features, so I'm unsure why they aren't working?

Edit:

I'm not sure if this is suppose to happen but, when I log my Venue require it returns an empty object {}.

console.log  (Venue) // This returns {} ???

Upvotes: 26

Views: 80059

Answers (3)

Suresh
Suresh

Reputation: 1

I had faced similar issue, after checking all the workaround finally issue got resolved by deleting the node_modules folder and run npm i.

Upvotes: -1

Blaskovicz
Blaskovicz

Reputation: 6160

In my instance, it was the same issue as @James111 was experiencing (circular import) due to a factory pattern I was trying to set up in Typescript. My fix was to do move the code into files, similar to the following:

// ./src/interface.ts
import { ConcreteClass } from './concrete';

export interface BaseInterface {
   someFunction(): any;
}

export class Factory {
  static build(): BaseInterface {
     return new ConcreteClass();
  }
}

// ./src/base.ts
import { BaseInterface } from './interface';
class BaseClass implements BaseInterface {
  someFunction(): any {
    return true;
  }
}

// ./src/concrete.ts
import { BaseClass } from './base';
export class ConcreteClass extends BaseClass {
  someFunction(): any {
    return false;
  }
}

Upvotes: 6

James111
James111

Reputation: 15903

So it turns out I had a circular reference in my code, where I was importing the class that was extending, into the class that itself was extending (tongue twister :P).

The obvious fix was to simply remove the extends reference and find another way of doing what I was trying to achieve. In my case it was passing the Venue class properties down into the VenueViews constructor.

E.g var x = VenueViews(this)

Upvotes: 53

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