App.js

import React,{useState, useReducer} from 'react'
import FunctionContextComponent from './components/FunctionContextComponent'
import {ThemeProvider} from "./ThemeContext";

export const ThemeContext = React.createContext()
export default function UseContextDemo(){
  return(
    <>
      <ThemeProvider>
        <FunctionContextComponent/>
      </ThemeProvider>
    </>
  )
}