🚀 go-pugleaf

Peter's solution is very helpful but I found it difficult to use with 'fontStyle' in addition in my case. So I try to do it like this:

var inputFilePathName = "/c/fileWithMissingFonts.inx";
var outputFilePathName = "/c/fileWithOutMissingFonts.inx";

// open document
var myFile = File(inputFilePathName);
var myDocument = app.open(myFile);

var defFont = app.fonts.item("Arial");
ReplaceMissingFont(myDocument, pageN, defFont);	

// save new doc
myDocument.exportFile(ExportFormat.indesignInterchange, new File(outputFilePathName));
myDocument.close(SaveOptions.no);

//-----------------------------------------------------
function ReplaceMissingFont(doc, defFont)
{
  with(doc)
  {		
    try
    {
      if(textDefaults.appliedFont.status == FontStatus.notAvailable)
        textDefaults.font = defFont;
    }
    catch(error)
    {
      textDefaults.font = defFont;
    }

ItemsChangeFont(paragraphStyles, defFont);
    ItemsChangeFont(characterStyles, defFont);

for (j=0; j < masterSpreads.length; j++) { ReplaceTextMissingFont(masterSpreads[j], defFont);	 } } ReplaceTextMissingFont(doc, defFont);	 }

function ReplaceTextMissingFont(doc, defFont)
{
  //document or masterSpread
  with(doc)
  {		
    for (i=0; i < allPageItems.length; i++) { if (allPageItems[i] == "[object TextFrame]") { with (allPageItems[i]) { ItemsChangeFont(paragraphs, defFont);	 ItemsChangeFont(textStyleRanges, defFont); } } } }

function ItemsChangeFont(items, defFont)
{	
  //Paragraphs or TextStyleRanges
  for (k=0; k < items.length ; k++) {	 with(items[k]) { //apply default font try { if (appliedFont && appliedFont.status == FontStatus.notAvailable) { appliedFont = defFont; appliedFont.fontStyle = "Regular"; }	 } catch(error){} } } }

Hope it may help somebody :)