Js实现监听input输入

实现原理：

默认input第一个带光标，第一个输完自动跳转到第一个输入框，以此类推，

当删除某一个输入框中的值重新输入，输入完后自动跳转到下一个

代码实现：

<div class="container">
  <h2>Verify Your Account</h2>
  <p>We emailed you the six digit code to cool_guy@email.com<br />Enter the code below to confirm your email address.</p>
  <div class="code-container">
     <input type="number" class="code" placeholder="0" min="0" max="9" required>
     <input type="number" class="code" placeholder="0" min="0" max="9" required>
     <input type="number" class="code" placeholder="0" min="0" max="9" required>
     <input type="number" class="code" placeholder="0" min="0" max="9" required>
     <input type="number" class="code" placeholder="0" min="0" max="9" required>
     <input type="number" class="code" placeholder="0" min="0" max="9" required>
  </div>
  <small class="info">THis is design only. We didn't actually send you an email as we don't have your email, right?</small>
</div>

let codes = document.querySelectorAll('.code')
codes[0].focus()
codes.forEach((code,idx) => {
    code.addEventListener('keydown', (e) =>{
        if(e.key >= 0 && e.key <=9) {
            codes[idx].value = ''
            setTimeout(() => codes[idx + 1].focus(), 10)
        }else if (e.key === 'Backspace') {
            setTimeout(() => codes[idx - 1].focus(), 10)
        }
    })
})

@import url('https://fonts.googleapis.com/css?family=Muli:300,700&display=swap');
*{
    box-sizing: border-box;
}
body{
    background: #fbfcfe;
    font-family: "Muli", sans-serif;
    display: flex;
    align-items: center;
    justify-content: center;
    height: 100vh;
    overflow: hidden;
    margin: 0;
}
.container{
    padding: 30px;
    background: #fff;
    border: 3px solid #000;
    border-radius: 10px;
    max-width: 1000px;
    text-align: center;
}
.code-container{
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 40px 0;
}
.code{
    border-radius: 5px;
    font-size: 75px;
    height: 120px;
    width: 100px;
    border: 1px solid #eee;
    margin: 1%;
    text-align: center;
    font-weight: 300;
    -moz-appearance: textfield;
}
.code::-webkit-outer-spin-button,
.code::-webkit-inner-spin-button{
    -webkit-appearance: none;
    margin: 0;
}
.code:valid{
    border: #3498bd;
    box-shadow: 0 10px 10px -5px rgba(0, 0, 0, 0.25);
}
.info{
    background: #eaeaea;
    display: inline-block;
    padding: 10px;
    line-height: 20px;
    max-width: 400px;
    color: #777;
    border-radius: 5px;
}
@media(max-width:600px){
    .code-container{
        flex-wrap: wrap;
    }
    .code{
        font-size: 60px;
        height: 80px;
        max-width: 70px;
    }
}

效果实现：