[Solved] Difference between previous row

by


Wrap the non-header rows in <tbody></tbody>.

Then use Array#prototype.reduce() to scan the rows in reverse, treating the first (ie last) row as a special case :

$("table tbody tr").get().reverse().reduce(function(prevVal, tr, i) {
    var $tds = $(tr).find('td'),
        val = Number($tds.eq(1).text().replace(',',''))
		diff = val - prevVal;
    // console.log(val);
    $tds.eq(2).text((i > 0) ? diff : '-');
    $tds.eq(3).text((i > 0) ? ((100 * diff / prevVal).toFixed(1) + '%') : '-');
	return val;
}, 0);
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<table>
  <tr>
    <th>Year</th>
    <th>Total</th>
    <th>Diff</th>
    <th>Percentage</th>
  </tr>
  <tbody>
  <tr>
    <td>2017</td>
    <td>80,000</td>
    <td>?</td>
    <td>?</td>
  </tr>

  <tr>
    <td>2016</td>
    <td>65,000</td>
    <td>?</td>
    <td>?</td>
  </tr>

  <tr>
    <td>2015</td>
    <td>59,000</td>
    <td>?</td>
    <td>?</td>
  </tr>

  <tr>
    <td>2014</td>
    <td>32,000</td>
    <td>?</td>
    <td>?</td>
  </tr>
  </tbody>
</table>

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solved Difference between previous row