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Exception Handling through JavaScript


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Exception Handling through JavaScript

Exception handling is an important concept which is widely used in programming language. Exception handling is an important approach which is designed to handle unexpected occurrence of code error in programming language. In other word, Exception handling is occurrence of unexpected code error due to which the execution of program may be terminated.

There is a specific way to handle the exception in JavaScript. Try, catch and finally are used to handle the exception. Try contains those blocks of code there is probability to occurrence unexpected code error and when exception is raised then catch block catches that exception and handle that exception i.e. catch block contains exception handler code.   

Here I am giving a small example to how exception handles within the JavaScript code. Here I am taking two input number1 and number2 and print division result of these two numbers. 

   Example: How to handle exception through the JavaScript

<html>

<head>

<title>Exception Handling</title>

 <script type="text/javascript">

    function ClickEventResult() {

        var num1 = document.getElementById("TextBox1").value;

        var num2 = document.getElementById("TextBox2").value;

        try {

            if (num1 == "" || num2 == "") {

                //// throw the exception when textbox is empty, throw keyword is used for throw user execption

                throw "empty";

            }

            else {

                /// calculate division result

                var result;

                result = num1 / num2;

                //// result show with confirm pop up message box

                confirm(result);

            }

        }

        catch (Error) {

            if (Error == "empty") {

                /// exception catch when empty throw

                alert("Textbox cannot empty:" + Error);

            }

            else {

                //// exception occured when result calculated

                alert(Error);

            }

        }

    }

     

    </script>

</head>

<body>

    <form id="form1" runat="server">

    <div>

    <table style="width: 446px; height: 132px">

      <tr>

        <td class="style1">

         <asp:Label ID="Label1" runat="server" Text="Enter first Number:"></asp:Label>

        &nbsp;

        </td>

        <td>

        <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>

            <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server"

                ControlToValidate="TextBox1" ErrorMessage="*"></asp:RequiredFieldValidator>

            <asp:RangeValidator ID="RangeValidator1" runat="server"

                ControlToValidate="TextBox1" ErrorMessage="*" MaximumValue="999999"

                MinimumValue="0" Type="Integer"></asp:RangeValidator>

        </td>

      </tr>

       <tr>

        <td class="style1">

         <asp:Label ID="Label2" runat="server" Text="Enter Second Number:"></asp:Label>

        </td>

        <td>

        <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>

            <asp:RequiredFieldValidator ID="RequiredFieldValidator2" runat="server"

                ControlToValidate="TextBox2" ErrorMessage="*"></asp:RequiredFieldValidator>

            <asp:RangeValidator ID="RangeValidator2" runat="server"

                ControlToValidate="TextBox2" ErrorMessage="*" MaximumValue="999999"

                MinimumValue="0" Type="Integer"></asp:RangeValidator>

        </td>

      </tr>

      <tr>

         <td class="style1">

        

            &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

        

         </td>

         <td>

         <%-- ClickEventResult Call the javascript block when button clicked by client--%>

             <asp:Button ID="Button2" runat="server" Text="Division" OnClientClick="ClickEventResult();" />

                     </td>

      </tr>

    </table>

 

    </div>

    </form>

  </body>

</html>


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