Try...Catch

Try

{statements}

Throw errCode

Catch err

{statements}

[Finally

{statements}]

End Try

Description

The Try…Catch statement allows you to test a block of code for runtime errors. The Try block contains the code to be run, and the Catch block contains the code to be executed if an error occurs. The optional Finally block is executed whether there is an error or not.

An error can be created by something that gets executed (such as division by zero) or you can force an error using the Throw statement. When you force an error using Throw, supply an errCode which can be a number or a string.

The Catch block has the value of the runtime error or the Throw message you supplied in err.

Example (Basic)

Rem Try Example
'Try catches run time errors
Try
   Dim CurrLiab, CurrAssets 
   CurAssets=InputBox("Enter assets")
   If Not IsNumeric(CurAssets) Then Throw 1
   If CurAssets < 0 Then Throw "lessthan"
   CurLiab=InputBox("Enter liabilities")
   If CurLiab=0 Then Throw "Divide by Zero"
   If CurLiab < 0 Then
      Throw "Liabilities must be > 0"
   End If
   If Not IsNumeric(CurLiab) Then Throw 1
   Print CurAssets, CurLiab
   Print "Ratio:" & CurAssets/CurLiab
Catch err
   If err=1 Then err="Enter a number"
   If err="lessthan" Then
      err="Value must be >= 0"
   End if
   Print err
Finally 'this is optional
   Print "Done"
End Try

Example (JavaScript)

// Try Example
/* Try catches run time errors */

try {
  var CurrLiab, CurrAssets;
   CurAssets=prompt("Enter assets","");
   if(!(IsNumeric(CurAssets)) ){ throw 1; }
   if(CurAssets < 0) { throw "lessthan"; }
   CurLiab=prompt("Enter liabilities","");
   if(CurLiab==0) { throw "Divide by Zero"; }
   if(CurLiab < 0) {
      throw "Liabilities must be > 0";
   }
   if(!(IsNumeric(CurLiab) ) ){ throw 1; }
   NSB.Print(CurAssets+ " " + CurLiab);
   NSB.Print("Ratio:" + (CurAssets/CurLiab));
} catch(err) {
   if(err==1) { err="Enter a number"; }
   if(err=="lessthan") {
      err="Value must be >= 0";
   }
   NSB.Print(err);
} finally { //this is optional
   NSB.Print("Done");
}

Output

(depends on what values are input)
Done