How to handle exception in JavaScript?

In this article we will discuss how to handle exception in JavaScript. The exception may occur at run time due to errors such as referencing a variable or a method that is not defined. Below example program has method name addNumbers() but here I have mistakenly call as addNumber() I have missed letter ‘s’ .when a specific line in the try block causes as exception. It was handled immediately to the catch block skipping the rest of code in the try block.

Example:

<script type="text/javascript">

    try {

        // Referencing a function thatdoes not exist cause an exception

       document.write(addNumber());

        // Since the above line causes anexception, the following line will not be executed

       document.write("twonumber added sucess.");

    }

    // When an exception occurs, ittransferred to the catch block

    catch (e) {

       document.write("Description= " + e.description+ "<br/>");

       document.write("Message= " + e.message + "<br/>");

       document.write("Stack= " + e.stack + "<br/><br/>");

    }

    function addNumbers() {

        var firstNumber = parseFloat(document.getElementById("txtFirstNumber").value);

        if (isNaN(firstNumber)) {

           alert("Pleaseenter a valid number in the first number textbox");

            return;

        }

        var secondNumber = parseFloat(document.getElementById("txtSecondNumber").value);

        if (isNaN(secondNumber)) {

           alert("Pleaseenter a valid number in the second number textbox");

            return;

        }

       document.getElementById("txtResult").value = firstNumber + secondNumber;

    }

  </script>

Output: