Node.js require class with constructor parameter

Question

I have a class

class advertHandler {
    constructor(projects) {
        this.projects = projects;
    }

    getProject(name) {
        return this.projects[name];
    }
}


module.exports = new advertHandler(projects);

When I try to use it like this

const advertHandler = require('./advertHandler')(projectsArray);
advertHandler.getProject('test');

And it throws an exception, require is not a function, but without a constructor, everything is fine, so the question is how to use the class constructor with require?

Check this answer stackoverflow.com/questions/30689817/…

MyUserInStackOverflow
– MyUserInStackOverflow

2017-03-02 14:31:10 +00:00
Commented Mar 2, 2017 at 14:31 — MyUserInStackOverflow
– MyUserInStackOverflow, Commented Mar 2, 2017 at 14:31

T.J. Crowder · Accepted Answer · 2021-11-25 10:57:44Z

26

It's not saying require is not a function, it's saying require(...) is not a function. :-) You're trying to call the result of require(...), but what you're exporting (an instance of advertHandler) isn't a function. Also note that in advertHandler.js, you're trying to use a global called projects (on the last line); ideally, best not to have globals in NodeJS apps when you can avoid it.

You just want to export the class:

module.exports = advertHandler;

...and then probably require it before calling it:

const advertHandler = require('./advertHandler');
const handler = new advertHandler({test: "one"});
console.log(handler.getProject('test'));

E.g.:

advertHandler.js:

class advertHandler {
    constructor(projects) {
        this.projects = projects;
    }

    getProject(name) {
        return this.projects[name];
    }
}

module.exports = advertHandler;

app.js:

const advertHandler = require('./advertHandler');
const handler = new advertHandler({test: "one"});
console.log(handler.getProject('test'));

edited Nov 25, 2021 at 10:57

answered Mar 2, 2017 at 11:07

T.J. Crowder

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2 Comments

A-letubby Over a year ago

Is it possible to do in single line? something like const advertHandler = new require('./advertHandler')({test: "one"});

T.J. Crowder Over a year ago

@A-letubby: Yes, but it's less readable: const handler = new (require('./advertHandler'))({test: "one"}); (note the () around the require call).

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