Serialising a HTML table to CSV format

html-table-to-csv.js

'use strict';

const { parseHTML } = require('linkedom');

const createSerialiser = serialiser =>
    element => {
        let result = '';

        const traverse = el => {
            const serialisedEl = serialiser(el, result.length);

            if (serialisedEl) {
                result += serialisedEl;
            }

            for (const child of Array.from(el.children)) {
                traverse(child);
            }

            return `${result}\n`;
        };

        return traverse(element);
    };

const createLineSerialiser = () => createSerialiser(
    (el, len) => ['th', 'td'].includes(el.tagName.toLowerCase())
        && `${len ? ',' : ''}${el.textContent}`
);

const serialiseTree = createSerialiser(
    el => el.tagName.toLowerCase() === 'tr' && createLineSerialiser()(el)
);

const table = `
    <table>
        <colgroup span="4"></colgroup>
        <tr>
          <th>Countries</th>
          <th>Capitals</th>
          <th>Population</th>
          <th>Language</th>
        </tr>
        <tr>
          <td>USA</td>
          <td>Washington, D.C.</td>
          <td>309 million</td>
          <td>English</td>
        </tr>
        <tr>
          <td>Sweden</td>
          <td>Stockholm</td>
          <td>9 million</td>
          <td>Swedish</td>
        </tr>
    </table>
`;

const { document } = parseHTML(table);

const tableElement = document.querySelector('table');

console.log(serialiseTree(tableElement));