The source of SpreadsheetDB used in the "Writing a Mail Merge in Google Apps Script" post on blog.davidbieber.com

spreadsheet.gs

function getColumnIndexes(columns) {
  // Returns a map from column name to column index.
  var container = {};
  for (var i = 0; i < columns.length; i++) {
    var value = columns[i];
    container[value] = i;
  }
  return container;
}

function getColumnIndexesFromSheet(sheet) {
  // Returns a map from column name to column index.
  var columnNames = getColumnNames(sheet);
  return getColumnIndexes(columnNames);
}

// Spreadsheet utilities
function getSheetByName(spreadsheet, name) {
  // Return a sheet from the provided spreadsheet with the given name.
  // Use SpreadsheetApp to get a spreadsheet.
  return spreadsheet.getSheetByName(name);
}

function getColumnNames(sheet) {
  // Gets the column names from the provided sheet.
  return sheet.getRange(1, 1, 1, sheet.getLastColumn()).getValues()[0];
}

function getRowWithColumnValue(sheet, columnIndex, value) {
  // Gets the values corresponding to the last row with columnIndex matching value.
  return getRowRangeWithColumnValue(sheet, columnIndex, value).getValues()[0];
}

function getRowRangeWithColumnValue(sheet, columnIndex, value) {
  // Gets the Range corresponding to the last row with columnIndex matching value.
  var condition = function(x) { return x == value; };
  return getRowRangeWithColumnSatisfying(sheet, columnIndex, condition);
}

function getRowRangeWithColumnSatisfying(sheet, columnIndex, condition) {
  // Gets the Range corresponding to the last row with columnIndex satisfying the condition function.
  var firstRow = 2;
  // Get a single column of values.
  var values = sheet.getRange(firstRow, columnIndex + 1, sheet.getLastRow()).getValues();
  for (var i = values.length - 1; i >= 0; i--) {
    var row = values[i];
    if (condition(row[0])) {
      return getRowRange(sheet, i + firstRow);
    }
  }
}

function updateRowWithColumnValue(sheet, columnIndex, value, newColumnIndex, newValue) {
  // Updates the last row with columnIndex matching value to use the newValue in newColumnIndex.
  var range = getRowRangeWithColumnValue(sheet, columnIndex, value);
  var values = range.getValues();
  values[0][newColumnIndex] = newValue;
  range.setValues(values);
}

function updateRowWithColumnSatisfying(sheet, columnIndex, condition, newColumnIndex, newValue) {
  // Updates the last row with columnIndex satisfying the condition fn to use the newValue in newColumnIndex.
  var range = getRowRangeWithColumnSatisfying(sheet, columnIndex, condition);
  var values = range.getValues();
  values[0][newColumnIndex] = newValue;
  range.setValues(values);
}

function forEachRow(sheet, doFn) {
  // Perform the doFn for each row in the spreadsheet.
  return forEachRowSatisfying(sheet, function(row) { return true; }, doFn);
}

function forEachRowSatisfying(sheet, condition, doFn) {
  // Perform the doFn for each row in the spreadsheet satisfying the condition fn.
  var firstRow = 2;
  // Get a single column of values.
  var range = sheet.getRange(/*row=*/firstRow, /*column=*/1,
                             /*numRows=*/sheet.getLastRow() - firstRow + 1, /*numColumns=*/sheet.getLastColumn());
  var values = range.getValues();
  var update = false;
  for (var i = values.length - 1; i >= 0; i--) {
    var row = values[i];
    if (condition(row)) {
      Logger.log(i);
      var newRow = doFn(row);
      if (newRow) {
        update = true;
        values[i] = newRow;
      }
    }
  }
  if (update) {
    range.setValues(values);
  }
}

function randomRow(sheet) {
  var rowNumber = randint(2, sheet.getLastRow());
  return getRow(sheet, rowNumber);
}

function getRow(sheet, row) {
  return getRowRange(sheet, row).getValues()[0];
}

function getRowRange(sheet, row) {
  return sheet.getRange(row, 1, /*numRows=*/1, /*numColumns=*/sheet.getLastColumn());
}

function addRow(sheet, row) {
  sheet.appendRow(row);
}

function randint(min, max) {
  // inclusive
  return Math.floor(Math.random() * (max - min + 1)) + min;
}