JavaScript Onchange获得返回

我有3个输入

Grand Total Box

<input type="text" name="GrandTotal" id="GrandTotal" class=" form-control" placeholder="Grand Total"  required />

首付款

<input type="text" name="DownPayment" id="downpayment" class=" form-control" placeholder="Down Payment" required />

状态框

 <input type="text" name="Status" id="status" class="form-control" placeholder="Status">

因此，使用JavaScript自动填充了总的总输入，示例GrandTotal是 2500 ，然后我必须填写下付盒，当我输入（如 3000 ）时，状态必须说已付款。但是，当我们填补下付时，例如 2000 状态必须说减去500

但现实是当我写下付款数字 5 时，它说还清了，甚至没有更改，即使我放了超过孙子的价值。但是当我删除值时，它说未定义

这是我的脚本

$('#downpayment').on('keyup keydown', function (
       var $this = $(this),
            GrandTotal = $("#GrandTotal").val(),
            downpayment = $("#downpayment").val();
          var  value = GrandTotal - downpayment;
            if (GrandTotal < downpaymentval) {
              var status = "PAID OFF";
            $('#status').val(status);
            } else {
              var status = "MINUS".value;
            $('#status').val(status);
            }
            console.log(status);
    });

谢谢，现在已经解决了，谢谢您回答

您的代码中有一些错字。当您获得数字并清空status字段时，我添加了一些parseFloat。

$("#downpayment").on("keyup keydown", function () {
    var $this       = $(this),
        GrandTotal  = parseFloat($("#GrandTotal").val()),
        downpayment = parseFloat($("#downpayment").val());
    // Empty status field
    $("#status").val("");
    // Returns if undefined
    if (!downpayment || !GrandTotal) {
        return;
    }
    // Your code
    var value = GrandTotal - downpayment;
    if (GrandTotal < downpayment) {
        var status = "PAID OFF";
        $("#status").val(status);
    } else {
        var status = "MINUS " + value;
        $("#status").val(status);
    }
    console.log(status);
});

<input type="text" name="GrandTotal" id="GrandTotal" class=" form-control" placeholder="Grand Total" required />
<input type="text" name="DownPayment" id="downpayment" class=" form-control" placeholder="Down Payment" required />
<input type="text" name="Status" id="status" class="form-control" placeholder="Status">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

您需要将字符串转换为float，然后才能比较它们。这可以使用parseFloat

完成

GrandTotal = parseFloat($("#GrandTotal").val());
downpayment = parseFloat($("#downpayment").val());

请参阅此处的JSFIDDLE

我已经为问题创建了解决方案，

<input type="text" name="GrandTotal" id="GrandTotal" class=" form-control" placeholder="Grand Total"  required />
    <input type="text" name="DownPayment" id="downpayment" class=" form-control" placeholder="Down Payment" required />
    <input type="text" name="Status" id="status" class="form-control" placeholder="Status">
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script> 
    <script type="text/javascript">
        $('#downpayment').on('keyup keydown', function () {
            var $this = $(this);
            var GrandTotal = parseInt($("#GrandTotal").val());
            var downpayment = parseInt($("#downpayment").val());
            var value = GrandTotal - downpayment;
            if (GrandTotal <= downpayment) {
                var status = "PAID OFF";
                $('#status').val(status);
            } else {
                var status = "MINUS" + value;
                $('#status').val(status);
            }
            console.log(status);
        });
    </script>

谢谢

您正在检查downpaymentval，但该变量不在您显示的代码中。应该是value吗？

您还使用了一个点来连接字符串而不是加法符号。

尝试以下内容：

$('#downpayment').on('keyup keydown', function (
   var $this = $(this), status,
        GrandTotal = $("#GrandTotal").val(),
        downpayment = $("#downpayment").val(),
        value = GrandTotal - downpayment;
        if (GrandTotal < value) {
          status = "PAID OFF";
        $('#status').val(status);
        } else {
          status = "MINUS" + value;
        $('#status').val(status);
        }
        console.log(status);
});

您还会注意到我已经将status变量的声明移至顶部。如果/其他语句，JavaScript不会更改内部范围，因此您不应两次声明它。

尝试解析数值为.val（）给出字符串对象。

$('#downpayment').on('keyup keydown', function (
       var $this = $(this),
            GrandTotal = $("#GrandTotal").val(),
            downpayment = $("#downpayment").val();
          var  value = GrandTotal - downpayment;
            if (parseInt(GrandTotal) < parseInt(downpaymentval)) {
              var status = "PAID OFF";
            $('#status').val(status);
            } else {
              var status = "MINUS".value;
            $('#status').val(status);
            }
            console.log(status);
    });

您的代码上有很多错误。请参阅下面的更新代码。

<input type="number" name="GrandTotal" id="GrandTotal" class=" form-control" placeholder="Grand Total"  required />
		<input type="number" name="DownPayment" id="downpayment" class=" form-control" placeholder="Down Payment" required />
		<input type="text" name="Status" id="status" class="form-control" placeholder="Status">
		<script src="https://code.jquery.com/jquery-3.2.1.min.js"></script>
		<script>
			$('#downpayment').on('keyup keydown', function (){
			
		       var $this = $(this),
		            GrandTotal = $("#GrandTotal").val(),
		            downpayment = $("#downpayment").val();
		          var  value = GrandTotal - downpayment;
		          var status = '';
		            if (GrandTotal < downpayment) {
		              status = "PAID OFF";            
		            } else {
		              status = "MINUS" + value;           
		            }
		            $('#status').val(status);
		            console.log(status);
		    });
		</script>

尝试以下代码：

$('#downpayment').on('keyup keydown', function (){
var $this = $(this),
GrandTotal = parseFloat($("#GrandTotal").val()),
downpayment = parseFloat($("#downpayment").val());
var value = GrandTotal - downpayment;
var status = '';
if (GrandTotal < downpayment) {
  status = "PAID OFF";
} else {
  status = "MINUS " + value;
}
$('#status').val(status);
});

$('#downpayment').on('keyup', function (){
        var grandTotal = $("#GrandTotal").val();
        var downpayment = $("#downpayment").val();
        grandTotal = grandTotal == undefined || grandTotal.length == 0?0:parseFloat(grandTotal);
        downpayment = downpayment == undefined || downpayment.length == 0?0:parseFloat(downpayment);
        var  value = grandTotal - downpayment;
        var status = value<0?"PAID OFF":"MINUS " + value;
        $('#status').val(status);
});

您的代码中有很多错误。未定义的变量，您没有将值转换为整数。我在这里解决了。

https://codepen.io/anon/pen/jmeazw

$(document).ready(function() {
    $('#downpayment').on('keydown', function () {
        GrandTotal = $("#GrandTotal").val();
        downpayment = $("#downpayment").val();
        GrandTotal = parseInt(GrandTotal);
        downpayment = parseInt(downpayment);
        var  value = parseInt(GrandTotal) - parseInt(downpayment);      
        var status = '';
        if (GrandTotal < downpayment) {
            status = "PAID OFF";
            $('#status').val(status);              
        } else {
            status = "MINUS " + value;            
            $('#status').val(status);
        }
    console.log(status);
});

}）;

您的代码中有一些错误。更改

1。 var status = "MINUS".value; to var status = "MINUS" + value;。

2。 $('#downpayment').on('keyup keydown', function ( to $('#downpayment').on('keyup keydown', function () {

更新的代码

$('#downpayment').on('change', function() {
  var GrandTotal = $("#GrandTotal").val(),
    downpayment = $("#downpayment").val();
  var value = GrandTotal - downpayment;
  if (GrandTotal <= downpayment) {
    var status = "PAID OFF";
    $('#status').val(status);
  } else {
    var status = "MINUS " + value;
    $('#status').val(status);
  }
  console.log(GrandTotal,downpayment,status);
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="text" name="GrandTotal" id="GrandTotal" class=" form-control" placeholder="Grand Total" required />
<input type="text" name="DownPayment" id="downpayment" class=" form-control" placeholder="Down Payment" required />
<input type="text" name="Status" id="status" class="form-control" placeholder="Status">

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