可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试):

问题:

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

How can I do this wherein if the user will enter a number for Num1, it will add it to Sum and dynamically change the displayed number in the Sum textbox. If the user will enter a number in Num2 it will also add that number to the updated number shown in Sum textbox and dynamically change the value for Sum textbox also.

How to do this in Javascript?

回答1:

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>

回答2:

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>

回答3:

<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.

回答4:

<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>

回答5:

<!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>