JSFiddle - React, Tailwind, and code Playground

HTML

<table>
    <table border="1">
    <tr>
    <th>**Code**</th>
    <th>**Days**</th>
    <th>**Date**</th>
    </tr>
    <tr>
    <td id="I Code">I</td>
    <td ><input type="number" value="0" onchange="update('row_1', this)"></td>    
    <td id="row_1">15/10/2017</td>
    </tr>
    </table>
    <input type="submit" value="Send">
    <input type="reset" value="Reset">
    <script>
    window.update = function update(id, el) {
      var x = el.value;
      var toAdd = 1000 * 60 * 60 * 24 * x;
      var time = new Date(new Date().getTime() + toAdd);
      console.log(time)
      var formattedDate = (time.getMonth()+1) + '/' + time.getDate() + '/' + time.getFullYear();
      document.getElementById(id).innerHTML = formattedDate;
    }
    </script>