What is the right way to use a class defined in one file and extend it another, in node.js?

Currently I have:

'use strict'

class BasePageHandler {

    constructor(app, settings, context) {

    }
}

return module.exports;

In the 'child' class file I have:

'use strict'

var BasePageHandler = require ('./../BasePageHandler.js');

class FrontpagePageHandler extends BasePageHandler {
    constructor(app, settings, context) {
         super(app, settings, context);
         this.settings = settings;
         this.context = context;
    }
}

This fails with the following error:

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

Note, if I have the BasePageHandler in the same file then it works, so it is really when the class is in another file I have an issue.

Currently using node 4.4.0.

What is the right way to use a class defined in one file and extend it another, in node.js?

Currently I have:

'use strict'

class BasePageHandler {

    constructor(app, settings, context) {

    }
}

return module.exports;

In the 'child' class file I have:

'use strict'

var BasePageHandler = require ('./../BasePageHandler.js');

class FrontpagePageHandler extends BasePageHandler {
    constructor(app, settings, context) {
         super(app, settings, context);
         this.settings = settings;
         this.context = context;
    }
}

This fails with the following error:

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

Note, if I have the BasePageHandler in the same file then it works, so it is really when the class is in another file I have an issue.

Currently using node 4.4.0.

• javascript
• node.js

• You may want to use ES6 native modules with the Common JS transform plugin for Babel, instead module.exports. That way, your code will stay future-ready for when Node implements modules natively. – Dan Dascalescu Commented Oct 3, 2016 at 1:51

2 Answers 2

You need to correctly export your class inBasePageHandler.js file:

module.exports = BasePageHandler;

The accepted answer is technically fine, but really if you're using ES6 then you should go all in and use ES6 export/import.

/*jshint esversion: 6 */

class BasePageHandler {
    constructor(app, settings, context) {
    }
}

export default BasePageHandler;

and then:

/*jshint esversion: 6 */

import BasePageHandler from './../BasePageHandler.js';

class FrontpagePageHandler extends BasePageHandler {
    constructor(app, settings, context) {
         super(app, settings, context);
         this.settings = settings;
         this.context = context;
    }
}