Adds custom text styles to Google Docs

custom-styles.js

let customStyles = {
  "code" : {
    "title" : "Code",
    "style" : {
      [DocumentApp.Attribute.FONT_FAMILY] : DocumentApp.FontFamily.CONSOLAS,
      [DocumentApp.Attribute.FONT_SIZE] : 11,
      [DocumentApp.Attribute.BACKGROUND_COLOR] : "#E8E8E8",
    },
  },
  "comic" : {
    "title" : "Comic Sans",
    "style" : {
      [DocumentApp.Attribute.FONT_FAMILY] : DocumentApp.FontFamily.COMIC_SANS_MS,
      [DocumentApp.Attribute.BACKGROUND_COLOR] : "#DDDDDD",
    },
  },
};

// https://stackoverflow.com/questions/64383424/set-anonymous-dynamic-functions-to-menu
(function IIFE(scope) {
  'use strict';
  for (let customStyleKey in customStyles) {
    let customStyle = customStyles[customStyleKey];
    let functionName = generateFormatTextFunctionName(customStyleKey);
    scope[functionName] = function () {
      formatText(customStyle.style);
    };
  }
})(this);

// Add new menu item
function onOpen() {
  let ui = DocumentApp.getUi();
  let menu = ui.createMenu("Custom Styles");
  for (let customStyleKey in customStyles) {
    let customStyle = customStyles[customStyleKey];
    let functionName = generateFormatTextFunctionName(customStyleKey);
    menu.addItem(customStyle.title, functionName);
  }
  menu.addToUi();
}

function generateFormatTextFunctionName(name, style) {
  return "formatText_" + name;
}

// https://webapps.stackexchange.com/questions/24249/how-do-i-add-new-styles-to-google-docs
function formatText(style) {
    var selection = DocumentApp.getActiveDocument().getSelection();
    if (selection) {
        var elements = selection.getRangeElements();
        for (var i = 0; i < elements.length; i++) {
            var element = elements[i];
            // Only modify elements that can be edited as text; skip images and other non-text elements.
            if (element.getElement().editAsText) {
                var text = element.getElement().editAsText();
                // Style the selected part of the element, or the full element if it's completely selected.
                if (element.isPartial()) {
                    text.setAttributes(element.getStartOffset(), element.getEndOffsetInclusive(), style);
                } else {
                    text.setAttributes(style);
                }
            }
        }
    }
}