compute sum dynamically with javascript

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I have two textboxes Num1 and Num2 and another textbox Sum having the value 10.

How can I do this wherein if the user

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5条回答

野趣味

2021-01-22 21:20

<!DOCTYPE html>
<html>
<head>

    <script type="text/javascript">
function calculate(){
    var x=parseInt(document.getElementById("first").value);
    var y=parseInt(document.getElementById("second").value);
    document.getElementById("answer").value=(x+y);
    }
    </script>

    <title>exam</title>
</head>

<body>
    <form>
        First:<input id="first" name="first" type="text"><br>
        Second:<input id="second" name="second" type="text"><br>
        Answer:<input id="answer" name="answer" type="text"><br>
        <input onclick="calculate()" type="button" value="Addition">
    </form>
</body>
</html>

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没有蜡笔的小新

2021-01-22 21:25

Something like that:

<input type="text" id="Num1" value="1" onblur="recalculateSum();"/>
<span>+</span>
<input type="text" id="Num2" value="1" onblur="recalculateSum();"/>
<span>=</span>
<input type="text" id="Sum" value=""/>
<script>

    function recalculateSum()
    {
        var num1 = parseInt(document.getElementById("Num1").value);
        var num2 = parseInt(document.getElementById("Num2").value);
        document.getElementById("Sum").value = num1 + num2;

    }

</script>

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慢半拍i

2021-01-22 21:31

<input type="text" id="Num1" name="Num1"/>
<input type="text" id="Num2" name="Num2"/>
<input type="text" id="Sum" name="Sum"/>


function addNums() {
  var num1 = parseInt(document.getElementById('Num1').value,10);
  var num2 = parseInt(document.getElementById('Num2').value,10)
  document.getElementById('Sum').value = (num1 + num2).toString();
}

There are other ways to reference the form items, but this one works.

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深忆病人

2021-01-22 21:34

<input type="text" id="Num1" value="1" onblur="recalculateSum();"/>

<input type="text" id="Num2" value="1" onblur="recalculateSum();"/>

<input type="text" id="Sum" value=""/>
<script>

    function recalculateSum()
    {
        var num1 = parseInt(document.getElementById("Num1").value);
        var num2 = parseInt(document.getElementById("Num2").value);
        document.getElementById("Sum").value = num1 + num2;

    }

</script>

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臣服心动

2021-01-22 21:40

Another version.


<!DOCTYPE html>
<html>
<head>
<title>Summer</title>
</head>
<body>
  Num 1: <input type="text" id="num1" name="num1" value="4"/><br />
  Num 2: <input type="text" id="num2" name="num2" value="6"/><br />
  Sum    <input type="text" id="sum"  name="sum" value="10">

<script type="text/javascript">
  var _num1 = document.getElementById('num1');
  var _num2 = document.getElementById('num2');
  var _sum  = document.getElementById('sum');

  _num1.onblur = function(){
    _sum.value = (parseInt(_sum.value,10) + parseInt(this.value,10));
  };
  _num2.onblur = function(){
    _sum.value = (parseInt(_sum.value,10) + parseInt(this.value,10));
  };  
</script>
</body>
</html>

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