List the fonts used in all the Illustrator files in a folder

list_used_fonts.jsx

/*
List the fonts
This shows you all the fonts used in all the Illustrator files in a folder,
even if the fonts aren't installed on your system.
You can then replace them with this script: https://gist.github.com/2778305
*/

function getAllFiles(folder) {
  var fileList = [];
  function recurse (folder) {
    var files = folder.getFiles("*.ai");
    for (var i = 0; i < files.length; i++)
      fileList.push(files[i]);

    var folders = folder.getFiles();
    var len = folders.length;
    for (var i = 0; i < len; i++) {
      if (folders[i] instanceof Folder) {
        recurse(folders[i]);
      }
    }
  }
  if (folder != null)
    recurse(folder);
  return fileList;
}

// collect the fonts
var sourceFolder = Folder.myDocuments.selectDlg( 'Select the folder with Illustrator files in which you want to replace fonts');
var files = getAllFiles(sourceFolder);

var fonts = [];
for ( var i = 0; i < files.length; i++ ) {
  var doc = app.open(files[i]);

  var frames = doc.textFrames;
  for ( var j = 0; j < frames.length; j++ ) {
    var ranges = frames[j].textRanges;

    range_loop:
    for ( var k = 0; k < ranges.length; k++ ) {
      var range = ranges[k];
      var family = range.characterAttributes.textFont.family;
      var style = range.characterAttributes.textFont.style;
      var entry = { 'family': family, 'style': style };

      var elen = fonts.length;
      for (var e = 0; e < elen; e++) {
        var dentry = fonts[e];
        if (entry.family == dentry.family && entry.style == dentry.style)
          continue range_loop;
      }
      fonts.push(entry);
    }
  }

  doc.close();  
}

// Adapted from the Illustrator Scripting Reference CS5 page 216
// Creates a new A3 sized document and display a list of available fonts until the document is full.
var edgeSpacing = 10;
var columnSpacing = 230;
var docPreset = new DocumentPreset;
docPreset.width = 1191.0;
docPreset.height = 842.0
var doc = documents.addDocument(DocumentColorSpace.CMYK, docPreset);

var labelRef = doc.textFrames.add();
if (labelRef) {
  labelRef.textRange.characterAttributes.size = 10;
  labelRef.contents = "Fonts used in "+sourceFolder.fullName;
  labelRef.top = doc.height - edgeSpacing;
  labelRef.left = edgeSpacing;
}

var fontName = "";
var x = edgeSpacing;
var y = (doc.height - edgeSpacing - 20);
var count = fonts.length;
for (var i = 0; i < count; i++) {
  //sFontName = ;
  //sFontName += " / ";
  fontName = fonts[i].family + " / " + fonts[i].style;
  var textRef = doc.textFrames.add();
  textRef.textRange.characterAttributes.size = 10;
  textRef.contents = fontName;
  textRef.top = y;
  textRef.left = x;
  
  // check wether the text frame will go off the edge of the document
  if ((x + textRef.width)> doc.width){
    textRef.remove();
    iCount = i;
    break;
  } else{
    // display text frame
    if( (y-=(textRef.height)) <= 20 ) {
      y = (doc.height - edgeSpacing - 20);
      x += columnSpacing;
    }
  }
}
redraw();

Hi,
The version of JavaScript (or ExtendScript) used by Adobe Illustrator is very different from the dialect you'll find anywhere else. It needs to be run directly inside Illustrator to get the APIs it needs.

That should then come up with some dialog boxes prompting you to pick a folder.

You may have more success with this version of the script:

https://github.com/dyslexic-charactersheets/scripts/blob/master/List%20used%20fonts%20to%20CSV.jsx

It relies on the Tools.jsxinc and underscore.js files, so download those together.