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Exception Handling Examples in JavaScript

Definition :

  It is an abnormal condition which terminates the program during its run time.

Types of exception handling :

Exception handlers are the keyboards which handles the exception during its runtime.

  • Try
  • Catch
  • Finally
  • Throw

Program :

<html>

     <head>

                     <script language=”javascript”>

                                    function display()

                                                {

                                                  a=10;

                                                  b=0;

                                                  c=a/b;

                                                  document.write(c);

                                                }

                                </script>

                </head>

                <body>

                     <input type=”button” value=”GetResult” onclick=”display()”/>

                </body>

</html>

Try :

It is a block of code which is meant for monitoring the statements for exceptions. It transfers the control to the catch block whenever an exception has been encountered in the program.

Catch :

Catch is a block of code which is meant for handling the exceptions writtened by the try block. catch block will take one parameter that is a variable which holds the information about the exceptions occurred in the program. For one try block at least one catch are finally block needs to be there.

Program :

<html>

     <head>

                     <script language=”javascript”>

                                    function display()

                                                {

                                                try

                                                {

                                                  a=10;

                                                  b=0;

                                                  c=a/d;

                                                  document.write(c);

                                                }

                                                catch(uuu)

                                                {

                                                alert(“invalid input”);

                                                console.log(uuu);

                                                console.error(uuu);

                                                }

                                                }

                                </script>

                </head>

                <body>

                     <input type=”button” value=”GetResult” onclick=”display()”/>

                </body>

</html>

Finally :

  Finally is the block of code which gets executed exactly once in the program life cycle.

Program :

<html>

   <head>

      <script language=”javascript”>

                      function display()

                                  {

                                     try

                                                 {

                                                 a=10;

                                                 b=2;

                                                 c=a/b;

                                                 document.write(c);

                                                 }

                                                   catch(err)

                                                   {

                                                   alert(“issue with application please try again”);

                                                   console.error(err);

                                                   }

                                                   finally {

                                                   alert(“END”);

                                                   }

                                  }

                                </script>

    </head>

                <body>

                  <input type=”button” value=”Get Result” onclick=”display()”/>

                </body>

</html>

Throw :

it is a keyword which is used for throwing the exceptions to the console based on the condition in exception handling.

Program :

<html>

   <head>

      <script language=”javascript”>

                      function display()

                                  {

                                                 a=10;

                                                 b=2;

                                                 if(b==0)

                                                 throw “invalid denominator”;

                                                 c=a/b;

                                                 document.write(c);

                                                 }

                                </script>

    </head>

                <body>

                  <input type=”button” value=”Get Result” onclick=”display()”/>

                </body>

</html>

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