September 17, 2002 - Nesting the try...catch Statement

Yehuda Shiran September 17, 2002
Nesting the try...catch Statement
Tips: September 2002

Yehuda Shiran, Ph.D.
Doc JavaScript

Let's look at another example that illustrates the multiple nesting levels of the try...catch...finally statements. Here is the code:

  function TryCatchDemo(x){
     try {
        try {
        if (x == null)                        
           throw "x equals null";            
        else
           throw "x does not equal null";   
        }
        catch(e) {                          
           if (e == "x equals null")          
              return(e + " and handled in inner catch block.");
          else                                
              throw e;                         
        }                                      
     }
     catch(e) {                               
        return(e + ", error handled in outer catch block."); 
     }
  }
  print(TryCatchDemo(null)+ "\n");
  print(TryCatchDemo(new Array(5)));
Notice that the finally statements are omitted, as they are only optional. We define the function TryCatchDemo() to act differently if its argument is null or not. If the argument is null, the error is handled in the inner catch block. If the argument is not null, the exception is handled in the outer catch block.

To learn more about exception handling, go to Column 118, JScript .NET, Part XII: Exception Handling.