Почему не работает калькулятор? На React

const Calc = () => {

let Input = document.querySelector('.num');

let Eq = document.querySelector('.eq');
let Multiply = document.querySelector('.multiply');
let Devide = document.querySelector('.devide');
let Plus = document.querySelector('.plus');
let Minus = document.querySelector('.minus');
let Ac = document.querySelector('.ac');
let Btns = document.querySelector('.buttons');
let Btn = document.querySelector('.btn');




let OneNumber = "";
let SecondNumber = "";
let OperationBtn = "";
let finish = false;

const numbers = ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "."];
const operations = ["+", "-", "*", "/"];

function clearAll() {
    OneNumber = "";
    SecondNumber = "";
    OperationBtn = "";
    finish = false;
    Input.textContent = "0";
}




Ac.addEventListener("click", clearAll);
Btns.addEventListener('click', function (event) {
    if (!event.target.classList.contains("btn")) return;

    Input.value = "";
    const key = event.target.textContent;

    if (numbers.includes(key)) {
        if (SecondNumber == "" && OperationBtn == "") {
        OneNumber += key;
        Input.textContent = OneNumber;
        }   else if (OneNumber !== "" && SecondNumber !== "" && finish) {
            SecondNumber = key;
            finish = false;
            Input.textContent = SecondNumber;

        }   else {
            SecondNumber += key;
            Input.textContent = SecondNumber;
        }
    }

    if (operations.includes(key)) {
        OperationBtn = key;
        Input.textContent = OperationBtn;
    }

    if (key == "=") {
        if (SecondNumber == "") SecondNumber = OneNumber;
        switch(OperationBtn) {
            case "+" :
             OneNumber = +OneNumber + +SecondNumber;
             break;
             case "-" :
             OneNumber = OneNumber - SecondNumber;
             break;
             case "*" :
             OneNumber = OneNumber * SecondNumber;
             break;
             case "/" :
             if (SecondNumber == "0") {
                Input.textContent = "Error";
             }
             OneNumber = OneNumber / SecondNumber;
             break;

        }
        finish = true;
        Input.textContent = OneNumber;
    }
})

};

export default Calc;

/*.app-wrapper {
  display: grid;
  width: 1200px;
  margin: 0 auto;

  grid-template-areas: 
  "h h"
  "n c";

  grid-template-rows: 60px 1fr;
  grid-template-columns: 2fr 10fr;
  grid-gap: 10px;
}

.header {
  grid-area: h;
  background-color: green;
}

.header img {
  width: 50px;
}

.nav {
  grid-area: n;
  background-color: burlywood;
}

.content {
  grid-area: c;
  background-color: cornflowerblue;
} */

.content {
  display: grid;
  border-radius: 10px;
  background-color: black;
  width: 240px;
  grid-gap: 50px;
}

.btn {
  background-color: #333;
  color: white;
  width: 50px;
  height: 50px;
  border-radius: 100%;
  margin-bottom: 7px;
}

.num {
  color: white;
  font-size: 40px;
  text-align: end;
  margin-right: 20px;
}

.buttons {
  margin-left: 8px;
  grid-gap: 10px;
  display: grid;
  grid-template-columns: 160px 0px;
}

.display {
  margin-top: -20px;
  height: 60px;
}

.btn:hover {
  background-color: #339;
}

.btn:active {
  background-color: #339;
}

import logo from './logo.svg';
import './App.css';
import Header from './components/Header';
import Navbar from './components/Navbar';
import Profile from './components/Profile';
import Calc from './my.js';

function App() {
  return (
    /*<div className="app-wrapper">
     <Header />
     <Navbar />
     <Profile />
    </div>*/
    <div>
        <div className="content">
            <div className="display">
                <p className="num">0</p>
            </div>
            <div className="buttons">
            <div className="numeral">
                <button className="btn one">1</button>
                <button className="btn two">2</button>
                <button className="btn three">3</button>
                <button className="btn four">4</button>
                <button className="btn five">5</button>
                <button className="btn six">6</button>
                <button className="btn seven">7</button>
                <button className="btn eight">8</button>
                <button className="btn nine">9</button>
                <button className="btn zero">0</button>
                <button className="btn eq">=</button>
                <button className="btn ac">ac</button>
                <button className="btn dot">.</button>
            </div>
            <div className="operation">
                <button className="btn multiply">*</button>
                <button className="btn devide">/</button>
                <button className="btn plus">+</button>
                <button className="btn minus">-</button>
            </div>
            </div>
        </div>
    </div>
  );
}



export default App;