JavaScripting InDesign

Many scripts encounter errors or unusual circumstances as they run. Sometimes, it is desirable for the script to simply stop in such circumstances reporting the error to the user for immediate attention. But in other situations it is better for a script to soldier on, simply logging its findings to a text file.

The function makeLogFile() facilitates this. It creates a text file (which, in truth could be used for anything) using the string aName as the basis for naming the file. The file is located in the same folder as the document passed in the argument aDoc. If aDoc is untitled, then the log file is created in the same folder as the script. The third argument (delete) is a Boolean. It determines whether the script should delete an existing file of the designated name or create a unique name based on the first argument.

function makeLogFile(aName, aDoc, deleteIt) {
  var logLoc; // path to folder that will hold log file
  try {
    logLoc = aDoc.filePath;
  } catch (e) {
    logLoc = getScriptPath().parent.fsName
  }
  var aFile = File(logLoc + "/" + aName + ".txt");
  if (deleteIt) {
    aFile.remove();
    return aFile;
  }
  var n = 1;
  while (aFile.exists) {
    aFile = File(logLoc + "/" + aName + String(n) + ".txt");
    n++
  }
  return aFile
}

Notice that this script depends on the function getScriptPath being available. It also doesn't actually create the log file, merely a file object. This means that a script which never actually logs anything won't create a log file. Here is the code I used to test this function:

//DESCRIPTION: Test making log file
myDoc = app.activeDocument;
log1 = makeLogFile("test",myDoc,true);
log(log1, "Text for log1 file");
log2 = makeLogFile("test",myDoc,false);
log(log2, "Text for log2 file");
log1.execute();
log2.execute();
function makeLogFile(aName, aDoc, deleteIt) {
  var logLoc; // path to folder that will hold log file
  try {
    logLoc = aDoc.filePath;
  } catch (e) {
    logLoc = getScriptPath().parent.fsName
  }
  var aFile = File(logLoc + "/" + aName + ".txt");
  if (deleteIt) {
    aFile.remove();
    return aFile;
  }
  var n = 1;
  while (aFile.exists) {
    aFile = File(logLoc + "/" + aName + String(n) + ".txt");
    n++
  }
  return aFile
}
function getScriptPath() {
  // This function returns the path to the active script, even when running ESTK
  try { 
    return app.activeScript; 
  } catch(e) { 
    return File(e.fileName); 
  }
}
function log(aFile, message) {
  var today = new Date();
  if (!aFile.exists) {
    // make new log file
    aFile.open("w");
    aFile.write(String(today) + "\nThe following messages were logged:\n");
    aFile.close();
  }
  aFile.open("e");
  aFile.seek(0,2);
  aFile.write("\n" + message);
  aFile.close();
}

Run this and two text files are opened, one named test.txt and one named test1.txt. That's because the first call has delete it set to true while the second has it set false. As a result, because we logged something to the log1 file before creating the log2 file object, two separate files were created.