你会做一个js获取验证码吗？

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>验证码</title>
    <style>
    .get{
        cursor: pointer;
    }
    .reset{
        display: none;
    }
    .reset span{
        color:red;
    }
    </style>
</head>
<body>
    <input type="text"><button>确定</button>
    <p class="get">获取验证码</p>
    <p class="reset">重新获取验证码<span>10</span>s</p>
</body>
<script>

function $(el) {
    return document.querySelector(el);
}
let val="";
let timer=null;
function stop() {
    clearInterval(timer);
    timer=null;
}
$(".get").onclick=function(){
    this.style.display="none";
    $(".reset").style.display="block";
    var chars = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K',
    'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'];
    function generateMixed(n) {
    var res = "";
    for(var i = 0; i < n; i++) {
       var id=Math.ceil(Math.random() * 35);
       res +=chars[id];
       }
       return res;
    }
    var num1=generateMixed(4);
    val=num1;
    alert(num1);
    var i=10;
    timer=setInterval(() => {
        i--;
        $(".reset span").innerText=i;
        if(i===0){
            stop();
            $(".reset").style.display="none";
            $(".get").style.display="block";
        }
    }, 1000);