Converts Google AppScript RichTextValue to HTML encoded strings.

richText2HTMLExample.js

/**
 * 2019 @mvogelgesang
 * This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.
 *
 * Gist: https://gist.github.com/mvogelgesang/8fe14931d79ed79d73154d969f02aada
 */

// Builds the new menu
function onOpen() {
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var menuEntries = [];
  menuEntries.push({name: "Run Script", functionName: "runScript"});
  ss.addMenu("RichText2HTML", menuEntries);  
}

function runScript() {
  var sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("CONFIG");
  var toEmail = sheet.getRange("b1").getValue();
  
  // simple error handling for e-mail address
  if (toEmail === "") {
    var ui = SpreadsheetApp.getUi();
    var response = ui.alert("Hey, an e-mail address is needed. Set the desired to address in CONFIG, cell B1");
    sheet.getRange("b1").activate();
    return;
  }
  
  var range = sheet.getRange("b2");
  var richText = range.getRichTextValue();
  
  MailApp.sendEmail({
    to: toEmail,
    subject: "I am trying out Apps Script!",
    htmlBody: htmlEncodeRichText(richText),
    body: richText.getText()
  });
}

/**
 * Given a RichTextValue Object, iterate over the individual runs
 *    and call out to htmlStyleRtRun() to return the text wrapped
 *    in <span> tags with specific styling.
 * @param {RichTextValue} richTextValue a RichTextValue object
 *    from a given Cell.
 * @return {string} HTML encoded text 
 */
function htmlEncodeRichText(richTextValue) {
  // create an empty string which will hold the html content
  var htmlString = "";
  // get an array of Runs for the given Rich Text
  var rtRuns = richTextValue.getRuns();
  // loop the array
  for (var i = 0; i < rtRuns.length; i++) {
    // return html version of a given run, append to existing string
    htmlString += htmlStyleRtRun(rtRuns[i]);
    Logger.log("Run # " + i + " plain text: ");
    Logger.log(rtRuns[i].getText());
    Logger.log("Run # " + i + " Output:");
    Logger.log(htmlString);
  }
  return htmlString;
}

/**
 * Given a RichTextValue Run, evaluates for style attributes and 
 *    builds a <span> tag with in-line styles. 
 *    For instance:
 *    <span style="color: cyan">text</span>
 *
 * @param {RichTextValue} richTextRun an instance of a
 *    RichTextValue run
 * @return {string} inputted text wrapped in <span> tag with 
 *    applicable styling. 
 */
function htmlStyleRtRun(richTextRun) {
  // string to hold the inline style key value pairs
  var styleString = "";
  // evaluate the attributes of a given Run and construct style attributes
  if (richTextRun.getTextStyle().isBold()) {
    styleString += "font-weight:bold;"
  }
  if (richTextRun.getTextStyle().isItalic()) {
    styleString += "font-style:italic;"
  }
  // fetch values for font family, size, and color attributes
  styleString += "font-family:" + richTextRun.getTextStyle().getFontFamily() +
    ";";
  styleString += "font-size:" + richTextRun.getTextStyle().getFontSize() +
    "px;";
  styleString += "color:" + richTextRun.getTextStyle().getForegroundColor() +
    ";";

  // underline and strikethrough use the same style key, text-decoration, must evaluate together, otherwise, the styling breaks. 
  // both false 
  if (!richTextRun.getTextStyle().isUnderline() && !richTextRun.getTextStyle().isStrikethrough()) {
    // do nothing
  }
  // underline true, strikethrough false
  else if (richTextRun.getTextStyle().isUnderline() && !richTextRun.getTextStyle()
    .isStrikethrough()) {
    styleString += "text-decoration: underline;";
  }
  // underline false, strikethrough true
  else if (!richTextRun.getTextStyle().isUnderline() && richTextRun.getTextStyle()
    .isStrikethrough()) {
    styleString += "text-decoration: line-through;";
  }
  // both true
  else {
    styleString += "text-decoration: line-through underline;";
  }

  // line breaks don't get converted, run regex and insert <br> to replace \n
  var richText = richTextRun.getText();
  var re = new RegExp("\n", "g");
  var richText = richText.replace(re, "<br>");

  // bring it all together
  var formattedText = '<span style="' + styleString + '">' + richText +
    '</span>';
  return formattedText;
}