This is a GAS library for copying the rich text with the text styles from Google Document to Google Spreadsheet or from Google Spreadsheet to Google Document using Google Apps Script (GAS). And, also the rich texts in the cells can be converted to HTML format.
Nice little helper library for copying rich text formatting from Google Docs and Sheets. You can view the project README for information on the formats that are currently supported. Personally, the inclusion of the
RichTextToHTMLForSpreadsheet method looks particularly useful for converting rich text formatting in Google Sheets cells to HTML for mail merge applications.