Try Catch in Javascript???????

var Text="";
function Alert()
{
try
  {
  alert("Welcome To Dotnetfunda!");
  }
catch(err)
  {
  Text="404 Error\n\n";
  Text+="Error description: " + err.message + "\n\n";
  Text+="Clik Yes \n\n";
  alert(Text);
  }