A set of functions for Google Sheets to sum columns by text formatting. Currently supports font weight, line-through, underline.

Code.gs

// These functions let's you sum columns based on their text formatting.
// The only flaw is that there's no text formatting change event, so you have to update the value of a field to trigger recalculation.

// styleRangeString (string) - The range where the text formatting should be evaluated. Example: A10:A20
// sumRangeString (string) - The range where the numerical values will be summed. Should correspond with styleRangeString unless you only specify column. Example: B10:B20 
// attribute (string) - The text formatting attribute for conditional check during sum.

// Note: styleRangeString and sumRangeString must be passed as a STRING, meaning it has to be wrapped in quotes ("A10:A20").

// Example:

// =sumIfFontStyle("A10:A20", "B", "italic")
// =sumIfFontWeight("A10:A20", "B", "bold")

// These will give the same result
// =sumIfLineStyle("A10:A20", "B", "line-through")
// =sumIfNotLineStyle("A10:A20", "B10:B20", "line-through")

// These will give the same result
// =sumIfLineStyle("A10:A20", "A", "line-through")
// =sumIfNotLineStyle("A10:A20", "A10:A20", "line-through")

function sumIfLineStyle(styleRangeString, sumRangeString, lineStyle) {
  return sumBase(styleRangeString, sumRangeString, (styleRange) => {
    return styleRange.getFontLines(); // https://developers.google.com/apps-script/reference/spreadsheet/range#getfontlines
  }, lineStyle, true);
}

function sumIfNotLineStyle(styleRangeString, sumRangeString, lineStyle) {
  return sumBase(styleRangeString, sumRangeString, (styleRange) => {
    return styleRange.getFontLines(); // https://developers.google.com/apps-script/reference/spreadsheet/range#getfontlines
  }, lineStyle, false);
}

function sumIfFontStyle(styleRangeString, sumRangeString, style) {
  return sumBase(styleRangeString, sumRangeString, (styleRange) => {
    return styleRange.getFontStyles(); // https://developers.google.com/apps-script/reference/spreadsheet/range#getfontlines
  }, style, true);
}

function sumIfNotFontStyle(styleRangeString, sumRangeString, style) {
  return sumBase(styleRangeString, sumRangeString, (styleRange) => {
    return styleRange.getFontStyles(); // https://developers.google.com/apps-script/reference/spreadsheet/range#getfontlines
  }, style, false);
}

function sumIfFontWeight(styleRangeString, sumRangeString, fontWeight) {
  return sumBase(styleRangeString, sumRangeString, (styleRange) => {
    return styleRange.getFontWeights(); // https://developers.google.com/apps-script/reference/spreadsheet/range#getfontlines
  }, fontWeight, true);
}

function sumIfNotFontWeight(styleRangeString, sumRangeString, fontWeight) {
  return sumBase(styleRangeString, sumRangeString, (styleRange) => {
    return styleRange.getFontWeights(); // https://developers.google.com/apps-script/reference/spreadsheet/range#getfontlines
  }, fontWeight, false);
}

function sumBase(styleRangeString, sumRangeString, getAttributes, attributeComparison, booleanComparison) {
  const { styleRangeObject, sumRangeObject } = handleRanges(styleRangeString, sumRangeString);
  const ss = SpreadsheetApp.getActiveSpreadsheet();
  const styleRange = ss.getRange(styleRangeObject.join(':'));
  const sumRange = ss.getRange(sumRangeObject.join(':')).getValues();
  const attributes = getAttributes(styleRange);
  let x = 0;
  for(var i = 0; i < attributes.length; i++) {
    if(
      (booleanComparison === true && attributes[i].toString() == attributeComparison)
      || booleanComparison === false && attributes[i].toString() != attributeComparison
    ) {
      try {
        const value = Number(sumRange[i].toString());
        if (!isNaN(value)){
          x += value;
        }
      } catch(e) {}
    }
  }
  return x;
}

function onEdit(e) {
  const ss = SpreadsheetApp.getActiveSpreadsheet();
  const ranges = ss.createTextFinder('(sumIfLineStyle|sumIfNotLineStyle|sumIfFontStyle|sumIfNotFontStyle|sumIfFontWeight|sumIfNotFontWeight)')
    .useRegularExpression(true)
    .matchFormulaText(true)
    .findAll();
  for(var i = 0; i < ranges.length; i++) {
    const formula = ranges[i].getFormula();

    const pattern = new RegExp(/(sumIfLineStyle|sumIfNotLineStyle|sumIfFontStyle|sumIfNotFontStyle|sumIfFontWeight|sumIfNotFontWeight)\("(?<styleRangeString>[A-Z0-9]+|[A-Z0-9]+:[A-Z0-9]+)";\s*"(?<sumRangeString>[A-Z0-9]+|[A-Z0-9]+:[A-Z0-9]+)";\s*"(.+)"\s*(|[^)]+)\)/);
    const matches = pattern.exec(formula);
    if (!matches || !matches?.groups) return;

    let { styleRangeString, sumRangeString } = matches.groups;
    const { styleRangeObject, sumRangeObject } = handleRanges(styleRangeString, sumRangeString);
    const styleRange = ss.getRange(styleRangeObject.join(':'));
    const sumRange = ss.getRange(sumRangeObject.join(':'));

    if(rangeIntersects(e.range, styleRange) || rangeIntersects(e.range, sumRange)) {
      ranges[i].setFormula('');
      SpreadsheetApp.flush();
      ranges[i].setFormula(formula);
    }
  }
}

function getLetter(string) {
  return string.replace(/[0-9]/g, ''); // Remove all numbers
}

function getNumber(string) {
  return string.replace(/\D/g,''); // Remove all but numbers
}

function isOnlyLetter(string) {
  return /^[A-Z]+$/.test(string);
}

function isLetterAndNumber(string) {
  return /^[A-Z0-9]+$/.test(string);
}

function handleRanges(styleRangeRaw, sumRangeRaw) {
  let styleRangeStart, styleRangeEnd, sumRangeStart, sumRangeEnd;
  const styleRangeArray = styleRangeRaw.split(':').map(e => e.trim().toUpperCase());
  const sumRangeArray = sumRangeRaw.split(':').map(e => e.trim().toUpperCase());

  // Set style range
  if (styleRangeArray.length === 1) {
    styleRangeStart = styleRangeArray[0];
    styleRangeEnd = styleRangeArray[0];
  } else {
    styleRangeStart = styleRangeArray[0];
    styleRangeEnd = styleRangeArray[1];
  }

  // Set sum range start
  sumRangeStart = sumRangeArray[0];
  if (isOnlyLetter(sumRangeStart)) {
    sumRangeStart = sumRangeStart + getNumber(styleRangeStart);
  }

  // Set sum range end
  if (sumRangeArray.length === 1) {
    if (isOnlyLetter(sumRangeArray[0])) {
      sumRangeEnd = getLetter(sumRangeStart) + getNumber(styleRangeEnd);
    } else {
      sumRangeEnd = sumRangeStart;
    }
  } else {
    sumRangeEnd = sumRangeArray[1];
    if (isOnlyLetter(sumRangeEnd)) {
      sumRangeEnd = sumRangeEnd + getNumber(styleRangeEnd);
    }
  }

  if (
    getLetter(styleRangeStart) != getLetter(styleRangeEnd)
    || getLetter(sumRangeStart) != getLetter(sumRangeEnd)
  ) {
    throw new Error('Range must have the same letter (no multi-column support).');
  }

  return {
    styleRangeObject: [styleRangeStart, styleRangeEnd],
    sumRangeObject: [sumRangeStart, sumRangeEnd]
  };
}

function rangeIntersects(R1, R2) {
  const LR1 = R1.getLastRow();
  const Ro2 = R2.getRow();
  if (LR1 < Ro2) return false;
  
  
  const LR2 = R2.getLastRow();
  const Ro1 = R1.getRow();
  if (LR2 < Ro1) return false;
  
  const LC1 = R1.getLastColumn();
  const C2 = R2.getColumn();
  if (LC1 < C2) return false;
  
  const LC2 = R2.getLastColumn();
  const C1 = R1.getColumn();
  if (LC2 < C1) return false;

  return true;
}