How to pass function as a prop in react typescript

Question

I am learning typescript with react and I occurred problem. I tried to pass function as a prop from my App component to child component named DataForm.

but I got an error:

Type '(f: any) => any' is not assignable to type '() => void'.
Parameter 'f' implicitly has an 'any' type.

And this is my code

App.tsx

 import React from 'react'; import './App.css'; import DataForm from './components/form'; export const Data = { name: "", country: "", age:"", adress:"" } function App() { const generateCard = ()=>{ console.log(" generateCard runned") } return ( <> <h1>Human Card Generator</h1> <DataForm createCard = { generateCard }/> </> ); } export default App;

components/form.tsx

 import React from 'react' import { Data } from '../App' import 'bootstrap'; interface dataFormProps{ createCard: ()=>void } export default function DataForm({ createCard = f => f }: dataFormProps){ const dataProceed = (e: any) =>{ Data.name = (document.getElementById('name') as HTMLInputElement).value; Data.country = (document.getElementById('country') as HTMLInputElement).value; Data.age = (document.getElementById('age') as HTMLInputElement).value; Data.adress = (document.getElementById('adress') as HTMLInputElement).value; createCard(); } return( <form onSubmit = { dataProceed }> <input type="text" id = "name" /> <input type="text" id = "country" /> <input type="number" id="age" /> <input type="text" id = "adress"/> <button type="submit">stwórz kartę</button> </form> ) }

Answer 1

The issue isn't when passing the function, it's when destructuring the props and providing a default function:

{ createCard = f => f }: dataFormProps

This code indicates that createCard should be a function which accepts a parameter and returns a value. Which it doesn't:

createCard: ()=>void

Make the default parameter match the signature:

{ createCard = () => {} }: dataFormProps

Answer 2

default function createCard should has type () => void . So just update like this:

DataForm({ createCard = () => {} }: dataFormProps)