console 命令行工具 X clear

console

    const reg = /^1\d{10}$/g;
    const msg = document.querySelector('.msg');
    const input = document.querySelector('input');

    input.oninput = function(){
      console.log(reg.test(this.value));
      if(reg.test(this.value)){
        msg.style.display = 'none';
      }else{
        msg.style.display = 'block';
      }
    }

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <div class="wrapper">
    <div class="phone">
      <span>手机号</span>
      <input type="text">
    </div>
    <div class="msg">手机号格式不正确</div>
  </div>

</body>
</html>

    .wrapper{
      margin: 40px;

    }
   .msg{
    color: red;
    margin-left: 50px;
   }