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How do I in javascript/asp add two textbox values and display in third? My code is below

 function fill() {
        var txt8 = document.getElementById("TextBox8").value;
        var txt9 = document.getElementById("TextBox9").value;
        document.getElementById("TextBox10").value = txt8 + txt9;


    }

I have onchange="fill" for both TextBox8 and TextBox9

How do I in javascript/asp add two textbox values and display in third? My code is below

 function fill() {
        var txt8 = document.getElementById("TextBox8").value;
        var txt9 = document.getElementById("TextBox9").value;
        document.getElementById("TextBox10").value = txt8 + txt9;


    }

I have onchange="fill" for both TextBox8 and TextBox9

• javascript
• asp

Share Improve this question Follow asked Oct 10, 2012 at 21:17 EM90210EM90210 14533 gold badges44 silver badges1313 bronze badges

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5 Answers 5

Sorted by: Reset to default 1

You have to call the function, onchange="fill()" notice the ()

why don't you use jQUery? Here is a sample:

function fill(){
var total=Number($('#TextBox9').val()) + Number($('#TextBox9').val());
$('#TextBox10').val(total);
}

    function Sum() {
        var text1 = document.getElementById('<%= TextBox1.ClientID %>');
        var text2 = document.getElementById('<%= TextBox2.ClientID %>');
        if (text1.value.length == 0 || text2.value.length == 0) {
            text1.value = 0;
            text2.value = 0;
        }

        var x = parseFloat(text1.value);
        var y = parseFloat(text2.value);          

        document.getElementById('<%= TextBox3.ClientID %>').value = x + y;
    }




<table>
    <tr>
        <td style="width: 100px">
            TextBox1</td>
        <td>
            <asp:TextBox ID="TextBox1" runat="server" onkeyup="Sum()"></asp:TextBox>
        </td>
    </tr>
    <tr>
        <td>
            TextBox2</td>
        <td>
            <asp:TextBox ID="TextBox2" runat="server" onkeyup="Sum()"></asp:TextBox>
        </td>
    </tr>
    <tr>
        <td>
            TextBox3</td>
        <td>
            <asp:TextBox ID="TextBox3" runat="server"></asp:TextBox>
        </td>
    </tr>
    <tr>
        <td>
            &nbsp;</td>
        <td>
            &nbsp;</td>
    </tr>
    <tr>
        <td>
            &nbsp;</td>
        <td>
            <asp:Button ID="Button1" runat="server" Text="Show" Width="80px" OnClientClick="Sum()" />
        </td>
    </tr>
</table>

Do you have a set of parentheses following the function call? In javascript if you don't follow a function call with parentheses it assumes you are referencing a variable. Also in the future if you are struggling to debug javascript code you should open up your browsers javascript console to see what is going on and what errors (if any) are thrown.

<input type="text" id="TextBox8" onchange="fill()" />

<input type="text" id="TextBox9" onchange="fill()" />

You need to convert string to integer. value always return string. jsfiddle

 <input onchange="fill()"  id=TextBox8 />
<input  onchange="fill()"  id=TextBox9 />
<input  id=TextBox10 /> 
<script>

    function fill() {
        var txt8 = document.getElementById("TextBox8").value-0;
        var txt9 = document.getElementById("TextBox9").value-0;
        document.getElementById("TextBox10").value = txt8 + txt9;


    }
</script>

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