Итоговый код календаря на JavaScript

Мой итоговый код к данному моменту:

html<div id="parent">
  <div id="calendar">
    <table>
      <thead>
        <tr>
          <th>пн</th>
          <th>вт</th>
          <th>ср</th>
          <th>чт</th>
          <th>пт</th>
          <th>сб</th>
          <th>вс</th>
        </tr>
      </thead>
      <tbody class="body"></tbody>
    </table>
  </div>
</div>

css#parent {
  text-align: center;
}
#calendar {
  display: inline-block;
}
#calendar td, #calendar th {
  padding: 5px 12px;
  border: 1px solid black;
  text-align: center;
}

javascriptlet calendar = document.querySelector('#calendar');
let body = calendar.querySelector('.body');
let prev = calendar.querySelector('.prev');
let next = calendar.querySelector('.next');

let date  = new Date();
let year  = date.getFullYear();
let month = date.getMonth();

draw(body, year, month);

function draw(body, year, month) {
  let arr = range(getLastDay(year, month));
  
  let firstWeekDay = getFirstWeekDay(year, month);
  let lastWeekDay  = getLastWeekDay(year, month);
  
  let nums = chunk(normalize(arr, firstWeekDay, 6 - lastWeekDay), 7);
  createTable(body, nums)
}

function createTable(parent, arr) {
  parent.textContent = '';
  let cells = [];
  
  for (let sub of arr) {
    let tr = document.createElement('tr');
    
    for (let num of sub) {
      let td = document.createElement('td');
      td.textContent = num;
      tr.appendChild(td);
      
      cells.push(td);
    }
    
    parent.appendChild(tr);
  }
  
  return cells;
}

function normalize(arr, left, right) {
  for (let i = 0; i < left; i++) {
    arr.unshift('');
  }
  for (let i = 0; i < right; i++) {
    arr.push('');
  }
  
  return arr;
}

function getFirstWeekDay(year, month) {
  let date = new Date(year, month, 1);
  let num  = date.getDay();
  
  if (num == 0) {
    return 6;
  } else {
    return num - 1;
  }
}

function getLastWeekDay(year, month) {
  let date = new Date(year, month + 1, 0);
  let num  = date.getDay();
  
  if (num == 0) {
    return 6;
  } else {
    return num - 1;
  }
}

function getLastDay(year, month) {
  let date = new Date(year, month + 1, 0);
  return date.getDate();
}

function range(count) {
  let arr = [];
  
  for (let i = 1; i <= count; i++) {
    arr.push(i);
  }
  
  return arr;
}

function chunk(arr, n) {
  let result = [];
  let count = Math.ceil(arr.length / n);
  
  for (let i = 0; i < count; i++) {
    let elems = arr.splice(0, n);
    result.push(elems);
  }
  
  return result;
}