<div class="main-out">
<p class="identifying-title">输入企业提供的验证码，即可完成签到</p>
<!--黑色横线框-->
<div class="pass-box">
<div class="pass-line">
<div class="line-box"><span class="line line-one"></span></div>
<div class="line-box"><span class="line line-two"></span></div>
<div class="line-box"><span class="line line-three"></span></div>
<div class="line-box"><span class="line line-four"></span></div>
<div class="line-box"><span class="line line-five"></span></div>
<div class="line-box"><span class="line line-six"></span></div>
</div>
<!--输入验证码框给一个绝对定位-->
<div class="passInput" id="on">
<input type="text" class="inputCont inputCont-one" maxlength="1" />
<input type="text" class="inputCont inputCont-two" maxlength="1"/>
<input type="text" class="inputCont inputCont-three" maxlength="1"/>
<input type="text" class="inputCont inputCont-four" maxlength="1"/>
<input type="text" class="inputCont inputCont-five" maxlength="1"/>
<input type="text" class="inputCont inputCont-six" maxlength="1"/>
</div>
</div>
</div>

.identifying-title{
width: 100%;
margin-top: 100px;
font-size: 14px;
color:#333;
text-align: center;
}
.pass-box{
position: relative;
width: 240px;
height: 40px;
margin: 50px auto 0;
}
.pass-line{
margin:0 auto;
width:100%;
height:100%;
}
.line-box{
float: left;
width: 40px;
height: 40px;
}
.line{
display: block;
width: 25px;
height:3px;
margin:18px auto 0;
background: #000;
}
.passInput{
position: absolute;
width:240px;
height:40px;
left: 0;
top: 0;
}
.inputCont{
float: left;
width: 25px;
height:40px;
margin:0 7.5px;
z-index: 2;
font-size:30px;
color:#333;
line-height: 40px;
text-align: center;
background: none;
}

<script type="text/javascript" src="js/jquery-2.1.4.min.js"></script>
<script>
$(function(){
//控制输入框只能输入一位并且是数字
$(".inputCont-one").focus();
$(".line-one").hide()
onload = function(){
var txts = on.getElementsByTagName("input");
for(var i = 0; i<txts.length;i++){
var t = txts[i];
t.index = i;
t.setAttribute("readonly", true);
t.onkeyup=function(){
if(this.value=this.value.replace(/\D/g,'')) {
var next = this.index + 1;
if(next > txts.length - 1) return;
txts[next].removeAttribute("readonly");
txts[next].focus();
}else{
$(this).focus();
}
}
}
txts[0].removeAttribute("readonly");
}
// 输入框获得焦点的时候后面的横线消失
$(".inputCont-one").focus(function(){
$(".line-one").hide()
})
$(".inputCont-two").focus(function(){
$(".line-two").hide()
})
$(".inputCont-three").focus(function(){
$(".line-three").hide()
})
$(".inputCont-four").focus(function(){
$(".line-four").hide()
})
$(".inputCont-six").focus(function(){
$(".line-six").hide()
})
$(".inputCont-five").focus(function(){
$(".line-five").hide()
})
})
</script>