parseNumber.js

import React, { useState } from "react";

const removeSymbol = num => (num.includes("+") ? num.replace(/\+/gi, "") : num);
const hasPrefix = num => num[0] == 2 ? num.substring(3) : num[0] == 0 ? num.substring(1) : num;

function App() {
  const [number, setNumber] = useState("");
  function parseNumber({ target: { value } }) {
    setNumber(value);
  }
  function validateNumber(e) {
    e.preventDefault();

    console.log(`260 ${hasPrefix(removeSymbol(number))}`);
  }
  return (
    <div className="App">
      <h1>Hello CodeSandbox</h1>
      <form onSubmit={validateNumber}>
        <input type="text" value={number} onChange={parseNumber} />
        <button type="submit">validate</button>
      </form>
    </div>
  );
}