JSFiddle - React, Tailwind, and code Playground

HTML

<table id=table>
    <col />
    <col span="2" />
    <col id="col-c" />
    <tr>
        <td>a</td><td colspan="2">b</td><td id=c>c</td>
    </tr>
</table>

<div id=log></div>

JavaScript

function getElementColumn(td)
    {
        var col = 0;
        $(td).parent().find('> td, > th').each(function() {
            if (this === td) return false;
            col += +$(this).attr('colspan') || 1;
        });
        return col;
    }

    function getCol(table, colNumber)
    {
        var col = 0, elem;
        $(table).find('> colgroup > col').each(function() {
            if (colNumber == col) {
                elem = this;
                return false;
            }
            col += +$(this).attr('span') || 1;
        });
        return elem;
    }

var colNumber = getElementColumn(document.getElementById('c'));
$('#log').append('<div>colNumber: ' + colNumber + '</div>');

var col = getCol(document.getElementById('table'), colNumber);
$('#log').append('<div>col: ' + col.id + '</div>');