JavaScript仿支付宝密码输入框

<div class="input"> 
<input type="tel" placeholder="随" maxlength=""><!- 
-><input type="tel" placeholder="机" maxlength=""><!- 
-><input type="tel" placeholder="" maxlength=""><!- 
-><input type="tel" placeholder="位" maxlength=""><!- 
-><input type="tel" placeholder="数" maxlength=""> 
</div> 

input { 
display: inline-block; 
&:last-child { 
border-right: px solid #; 
} 
input { 
border-: px solid #; 
border-bottom: px solid #; 
border-left: px solid #; 
width: px; 
height: px; 
outline:none; 
font-family: inherit; 
font-size: px; 
font-weight: inherit; 
text-align: center; 
line-height: px; 
color: #c; 
background: rgba(,,,); 
} 
}

/ 
 模拟支付宝的密码输入形式 
/ 
(function (window, document) { 
var active = , 
inputBtn = document.querySelectorAll('input'); 
for (var i = ; i < inputBtn.length; i++) { 
inputBtn[i].addEventListener('click', function () { 
inputBtn[active].focus(); 
}, false); 
inputBtn[i].addEventListener('focus', function () { 
this.addEventListener('keyup', listenKeyUp, false); 
}, false); 
inputBtn[i].addEventListener('blur', function () { 
this.removeEventListener('keyup', listenKeyUp, false); 
}, false); 
} 
/ 
 监听键盘的敲击事件 
/ 
function listenKeyUp() { 
var beginBtn = document.querySelector('#beginBtn'); 
if (!isNaN(this.value) && this.value.length != ) { 
if (active < ) { 
active += ; 
} 
inputBtn[active].focus(); 
} else if (this.value.length == ) { 
if (active > ) { 
active -= ; 
} 
inputBtn[active].focus(); 
} 
if (active >= ) { 
var _value = inputBtn[active].value; 
if (beginBtn.className == 'begin-no' && !isNaN(_value) && _value.length != ) { 
beginBtn.className = 'begin'; 
beginBtn.addEventListener('click', function () { 
calculate.begin(); 
}, false); 
} 
} else { 
if (beginBtn.className == 'begin') { 
beginBtn.className = 'begin-no'; 
} 
} 
} 
})(window, document);