A couple of helper functions I always use when automating workflow processes from Google Sheets in GAS.

helpers.gs

// Get a sheet from a given spreadsheet by the ID of the sheet
function getSheetById(spreadsheet, sheetId) {
  return spreadsheet.getSheets().filter(function(sheet) {return sheet.getSheetId() == sheetId})[0];
}

// Lowers and strips whitespace of an array or string
function lowerNoSpace(object) {
  var type = object.constructor.name;
  switch (type) {
    case "String":
      return object.toLowerCase().replace(/\s/g, '');
    case "Array":
      for (i in object) {
        object[i] = lowerNoSpace(object[i]);
      }
      return object; 
    default:
      return object;
  }
}

// returns a 1d array of column labels in column 1 from given sheet
function getColNames(sheet) {
  var numColumns = sheet.getLastColumn();
  return sheet.getRange(1, 1, 1, numColumns).getValues()[0]; //Object[][] is returned, we want just the first subarray/row
}

// gets row labels in row 1 from given sheet. 
function getRowNames(sheet) {
  var numRows = sheet.getLastRow();
  var firstCol2d = sheet.getRange(1, 1, numRows, 1).getValues();
  var rowNames = Array.prototype.concat.apply([], firstCol2d);
  return rowNames;
}

// finds a spreadsheet column index by using the column name in the first row in specified sheet. Return 0 on fail
function getColIndexByName(sheet, colName) {
  var firstRow = lowerNoSpace(getColNames(sheet));
  return firstRow.indexOf(lowerNoSpace(colName))+1;
}

// finds a spreadsheet row index by using the row name in the first column in specified sheet. Return 0 on fail
function getRowIndexByName(sheet, rowName) {
  var firstCol = lowerNoSpace(getRowNames(sheet));
  return firstCol.indexOf(lowerNoSpace(rowName))+1;
}

// gets the data from a cell at rowNum, columnNum in specified sheet
function getCellByRowNumColNum(sheet, rowNum, colNum) {
  return sheet.getRange(rowNum,colNum).getValue();
}

// gets the data from a cell at rowName, columnName in specified sheet
function getCellByRowNameColName(sheet, rowName, colName) {
  var row = getRowIndexByName(sheet, rowName);
  var col = getColIndexByName(sheet, colName);
  if (row==0 || col==0) {
    return "A cell with those row and column labels does not exist";
  }
  return getCellByRowNumColNum(sheet, row, col);
}