Cannot use 'callback' with fs, Typescript

Question

Yo, I have this peice of code in my API and it gives me an error I don't understand.

Code :

server.get('/deleteall', async (request, reply) => {
  var json = JSON.stringify(deleteall);
  fs.writeFile('todos.json', json, 'utf8', callback);
  return 'File overwritten.'
})

Error :

Argument of type '(arg0: string, json: string, arg2: string, callback: any) => void' is not assignable to parameter of type 'NoParamCallback'.

The error happens on build, I don't understand it at all, keep in mind, this is my first TS experience.

Robby Cornelissen · Accepted Answer · 2022-06-03 03:01:22Z

3

The callback argument for fs.write() is defined like this:

export type NoParamCallback = (err: NodeJS.ErrnoException | null) => void;

Whatever you have defined as callback does not match that type definition. It should be something like:

function callback(err) {
  console.log(err);
}

Or specified inline:

fs.writeFile('todos.json', json, 'utf8', (err) => console.log(err));

As a more general comment: I suggest you migrate to the promises API to escape callback hell.

edited Jun 3, 2022 at 3:01

answered Jun 3, 2022 at 2:27

Robby Cornelissen

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2 Comments

Zariaa_ Over a year ago

I followed this guide, here's my full code

Robby Cornelissen Over a year ago

Right. As I said: that callback method you define at the end does not match the expected signature.

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