<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0, user-scalable=no, minimal-ui">
<meta name="screen-orientation" content="portrait"/>
<meta name="apple-mobile-web-app-capable" content="yes">
<meta name="format-detection" content="telephone=no">
<meta name="full-screen" content="yes">
<meta name="x5-fullscreen" content="true">
<title>input</title>
<script src="https://cdn.bootcss.com/jquery/3.1.1/jquery.min.js"></script>
<style>
</style>
</head>
<body>
<input type="text" class="enter">
<input type="text" class="enter">
<input type="text" class="enter">
<input type="text" class="enter">
<input type="text" class="total">
<script>
$('.enter').keyup(function(event) {
var total = 0
var num = Number($(this).val())
var val = num === NaN ? 0 : num
$('.enter').each(function(data){
if(this == event.target) return
total += Number($(this).val())
})
$('.total').val(total + val)
})
</script>
</body>
</html>
