matrix-table.js

export default class MatrixTable {

  convert(table) {
    const array = this.createArray(table);
    const conversion = this.transpose(array);

    return this.createTable(conversion).outerHTML;
  }

  transpose(ary) {
    return Object.keys(ary[0]).map(c =>
      ary.map(r => r[c])
    );
  }

  createArray(table) {
    const array = [];
    const rowSpan = [];
    let columnCount = 0;
    [].forEach.call(table.querySelectorAll('tr'), (tr, i) => {
      const tdAry = [];
      const items = tr.querySelectorAll('td,th');
      const tdTh = Array.from(items);
      if (i === 0) {
        columnCount = items.length;
      }
      for (let k = 0; k < columnCount; k++) {
        if (parseInt(rowSpan[k], 10) > 0) {
          tdAry[k] = 'empty';
          rowSpan[k]--;
        } else {
          const item = tdTh.shift();
          const colSpan = item.getAttribute('colspan');
          rowSpan[k] = item.getAttribute('rowspan');
          if (colSpan) {
            item.removeAttribute('colspan');
            item.setAttribute('rowspan', colSpan);
          }
          if (rowSpan[k]) {
            item.removeAttribute('rowspan');
            item.setAttribute('colspan', rowSpan[k]);
          }
          tdAry[k] = item.cloneNode(true);
          if (parseInt(colSpan, 10) > 1) {
            for (let j = 1; j < colSpan; j++) {
              tdAry[k + j] = 'empty';
              k++;
            }
          }
        }
      }
      array[i] = tdAry;
    });
    return array;
  }

  createTable(array) {
    const table = document.createElement('table');
    array.forEach((items) => {
      const tr = document.createElement('tr');
      items.forEach((item) => {
        if (item !== 'empty') {
          tr.appendChild(item);
        }
      });
      table.appendChild(tr);
    });
    return table;
  }
}