Get column numbers from column names - Google apps scripts for spreadsheets

column_numbers_from_names.gs

// Pass the column headers range and names, and it will return an object with the relation between column names and column numbers
function getColumnNumbersForNames(sheetName, columnHeadersRangeA1Notation, columnNames){
  var thisSpreadsheet = SpreadsheetApp.getActiveSpreadsheet();
  var sheet = thisSpreadsheet.getSheetByName(sheetName);
  var columnHeadersRange = sheet.getRange(columnHeadersRangeA1Notation);
  var columnNamesOnSheet = flatten(columnHeadersRange.getValues());
  
  var columnNumbersForNames = {};
  for(var count = 0; count < columnNames.length; count++){
    var columnName = columnNames[count]
    columnNumbersForNames[columnName] = columnNamesOnSheet.indexOf(columnName) + 1
  }
  
  return columnNumbersForNames
}

Example:

// Returns an object:  { "Street Address": 4, "Name": 1 }
getColumnNumbersForNames("Clients", "A1:Z1", ['Street Address', 'Name'])