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Exception


Try/Catch Blocks

<html>
<head>
<script type="text/javascript">
var txt="";
function message()
{
try
  {
  adddlert("Welcome guest!");
  }
catch(err)
  {
  txt="There was an error on this page.\n\n";
  txt+="Error description: " + err.description + "\n\n";
  txt+="Click OK to continue.\n\n";
  alert(txt);
  }
}
</script>
</head>

<body>
<input type="button" value="View message" onclick="message()" />
</body>

</html>

Throw

<html>
<body>
<script type="text/javascript">
var x=prompt("Enter a number between 0 and 10:","");
try
  {
  if(x>10)
    {
    throw "Err1";
    }
  else if(x<0)
    {
    throw "Err2";
    }
  else if(isNaN(x))
    {
    throw "Err3";
    }
  }
catch(er)
  {
  if(er=="Err1")
    {
    alert("Error! The value is too high");
    }
  if(er=="Err2")
    {
    alert("Error! The value is too low");
    }
  if(er=="Err3")
    {
    alert("Error! The value is not a number");
    }
  }
</script>
</body>
</html>




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