React ) 리액트로 사업자번호 유효검사

import logo from './logo.svg';
import { useState } from 'react';
import './App.css';

function Main(){
    const validNumber = [1,3,7,1,3,7,1,3,5];
    const [businessNumArray, setBusinessNumArray] = useState([]);
    const [tempArray, setTempArray] = useState([]);
    //const [sum, setSum] = useState(null);
    
    return (
        <div>
            <form onSubmit={event=>{
                event.preventDefault();
                
                const businessNum = event.target.businessNum.value;
                for(let i=0; i<businessNum.length; i++){
                    setBusinessNumArray(businessNumArray.push(businessNum[i]));
                }
                let sum = 0;
                for(let i=0; i<businessNumArray.length-1; i++){
                    setTempArray(tempArray.push(validNumber[i] * Number(businessNumArray[i])));
                    sum += tempArray[i];
                }
                let last = Math.floor((validNumber[8] * businessNumArray[8]) / 10);
                let aa = (sum + last) % 10;
                aa = 10 - aa;
                if(aa==2){
                    alert("ok")
                } else{
                    alert("No")
                }
                
                // console.log(sum)
                // console.log(last)
                // console.log(aa)
                //console.log(aa)
            }}>
                <input name='businessNum' placeholder='사업자번호'></input>
                <input type='submit' placeholder='유효성검사'></input>
            </form>
            <div></div>
        </div>
    )
}
function App() {
    return (
        <div>
            <Main></Main>
        </div>
    );
}

export default App;