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4GuysFromRolla.com : ASP FAQS : Functions and Subroutines


Question:

How can I make an argument of a Function or Sub optional?


[Print this FAQ]

Answer: In VBScript, the Optional keyword (which allows some arguments to be left out in VB) is not implemented. This means that you must declare every argument that you want to use. What you can do is pass null values to your functions:

<%
  Function SomeArgs(one, two, three, four)
    SomeArgs = one & two & three & four
  End Function

  Response.Write SomeArgs(1, 2, 3, null)
  ' The above statement writes 123 to the browser
%>

Optionally, you can use an array-based method to fake optional parameters in VBScript. For more information on this technique be sure to read the article Optional Arguments in VBScript.

Optional Arguments in JScript
If you truly want to be able to pass or not pass arguments arbitrarily you can revert to JScript, which allows you to pass as few or as many arguments as you like:

<%@language=JScript%>
<%
  // Don't declare any arguments in the function declaration:
  function SomeArgs() {
    var strReturn = new String('');

    // Instead, use the intrinsic arguments object to retrieve arguments.
    // This loops through the arguments object appending the value of each
    // to the result:

    for (i=0; i<arguments.length; i++) {
      strReturn += arguments[i];
    }
    return(strReturn);
  }

  // Pass whatever arguments you like:
  Response.Write(SomeArgs('one' , 'two', 'three'));
  Response.Write('<br>');
  Response.Write(SomeArgs(1, 2, 3, 4, 5, 6, 7, 8));

  // Displays this:
  // onetwothree
  // 12345678
%>


FAQ posted by Richard Lowe at 10/4/2000 11:59:00 AM to the Functions and Subroutines category. This FAQ has been viewed 66,690 times.

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Last computed at 9/17/2007 3:22:00 AM


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