html table with javascript, array double to table html

Helper.js

function Helper() {
  function getCells(data, type) {
    return data.map(cell => `<${type} style="border: 1px solid #000;" >${cell}</${type}>`).join('');
  }

  function createBody(data) {
    return data.map(row => `<tr style="border: 1px solid #000;" >${getCells(row, 'td')}</tr>`).join('');
  }

  this.generateTable = (data) => {

    // Destructure the headings (first row) from
    // all the rows
    const [headings, ...rows] = data;

    // Return some HTML that uses `getCells` to create
    // some headings, but also to create the rows
    // in the tbody.
    return `
          <table style="width:100%; border: 1px solid black;border-collapse: collapse;text-align: left;" >
            <thead>${getCells(headings, 'th')}</thead>
            <tbody>${createBody(rows)}</tbody>
          </table>
        `;
  }
}

module.exports = Helper;

html table with javascript - usage.js

const Helper = require("./common/Helper.js")
var helper = new Helper();

var mailInbox = [];
//header
mailInbox.push(["to","subject","content","isHtml"])
//rows
mailInbox.push(["jane","message 1","hi 1","true"])
mailInbox.push(["kurt","message 2","hi 2","false"])
mailInbox.push(["rich","message 3","hi 3","true"])
//get html as string
helper.generateTable(mailInbox)