// Written by Amit Agarwal www.ctrlq.org

function writeJSONtoSheet(json) {
  var sheet = SpreadsheetApp.getActiveSheet();

  var keys = Object.keys(json).sort();
  var last = sheet.getLastColumn();
  var header = sheet.getRange(1, 1, 1, last).getValues()[0];
  var newCols = [];

  for (var k = 0; k < keys.length; k++) {
    if (header.indexOf(keys[k]) === -1) {
      newCols.push(keys[k]);
    }
  }

  if (newCols.length > 0) {
    sheet.insertColumnsAfter(last, newCols.length);
    sheet.getRange(1, last + 1, 1, newCols.length).setValues([newCols]);
    header = header.concat(newCols);
  }

  var row = [];

  for (var h = 0; h < header.length; h++) {
    row.push(header[h] in json ? json[header[h]] : '');
  }

  sheet.appendRow(row);
}