Remove unused styles from book documents at once.

Please check below code:

var myFileLocation = Folder.selectDialog("Please select path to files"); // file path selection
var myFolder = new Folder(myFileLocation);
var myFolderContents = myFolder.getFiles("*.indb"); // array
var myFileAmount = myFolderContents.length;

// Check if any .indb files were found
if (myFileAmount === 0) {
    alert("No INDB files found in the selected folder.");
} else {
    // Loop through the INDB files
    for (var i = 0; i < myFileAmount; i++) {
        var inFile = myFolderContents[i];
         app.scriptPreferences.userInteractionLevel = UserInteractionLevels.NEVER_INTERACT;
        // Open the INDB file
        var doc = app.open(inFile);
        app.scriptPreferences.userInteractionLevel = UserInteractionLevels.INTERACT_WITH_ALL;
        // Access the book contents
        var bookContents = doc.bookContents;
        
          // Loop through the book contents (individual documents in the book)
        for (var j = 0; j < bookContents.length; j++) {
            var bookItem = bookContents[j];
            
           var tempDoc = app.open(bookContents[j].fullName);
           
            var myDocument = app.activeDocument;
    
    
    var allCharacterStyles = myDocument.allCharacterStyles;
    
    // Loop through each character style
    for (var i = 0; i < allCharacterStyles.length; i++) {
      var style = allCharacterStyles[i];
      // Set the search criteria for the findText() method
      app.findTextPreferences = NothingEnum.nothing;
      app.findTextPreferences.appliedCharacterStyle = style;
      // Search entire document for instances of the character style
      var found = myDocument.findText();
      // If the style is not found in the document, delete it
      if (found.length == 0) {
        try {
          style.remove();
        } catch (e) {
          // Ignore the error
        }
      }
      // Reset the findTextPreferences object
      app.findTextPreferences = NothingEnum.nothing;
    }

    // Repeat the above for Paragraph Styles

    // Get all the paragraph styles in the document
    var allParagraphStyles = myDocument.allParagraphStyles;
    
    // Loop through each paragraph style
    for (var i = 0; i < allParagraphStyles.length; i++) {
      var style = allParagraphStyles[i];
      // Set the search criteria for the findText() method
      app.findTextPreferences = NothingEnum.nothing;
      app.findTextPreferences.appliedParagraphStyle = style;
      // Search entire document for instances of the style
      var found = myDocument.findText();
      // If the style is not found in the document, delete it
      if (found.length == 0) {
        try {
          style.remove();
        } catch (e) {
          // Ignore the errors
        }
      }
      // Reset the findTextPreferences object
      app.findTextPreferences = NothingEnum.nothing;
    }
}
}
}

var documents = app.documents;
for (var i = documents.length - 1; i >= 0; i--) {
    documents[i].close(SaveOptions.YES);
}
    app.activeBook.close(SaveOptions.YES);
    alert("Done");