DWfile.exists()

Availability 2.0
Description Tests for the existence of the specified file.
Arguments fileURL
The argument is the file you are looking for, expressed as a file:// URL.
Returns TRUE if the file exists, FALSE otherwise.
Example The following code checks for a file called mydata.txt and displays an alert box that tells the user whether the file exists or not. 
var fileURL = "file:///c|/temp/mydata.txt";
if (DWfile.exists(fileURL)){
  alert( fileURL + " exists!");
}else{
  alert( fileURL + " does not exist.");
}