http://www.gsi.go.jp/KOKUJYOHO/MOUNTAIN/mountain.html

sc.js

const { JSDOM } = require("jsdom");
const dom = new JSDOM(``, {
    url: "http://www.gsi.go.jp/KOKUJYOHO/MOUNTAIN/mountain.html",
    contentType: "text/html",
    includeNodeLocations: true,
    storageQuota: 10000000
});

function tableToJson(table) {
    const data = []; // first row needs to be headers var headers = [];
    const headers = [];
    for (let i = 0; i < table.rows[0].cells.length; i++) {
        headers[i] = table.rows[0].cells[i].textContent.trim();
    }
    // go through cells
    for (let i = 1; i < table.rows.length; i++) {
        const tableRow = table.rows[i];
        const rowData = {};
        for (let j = 0; j < tableRow.cells.length; j++) {
            const rowName = headers[j];
            const tableCell = tableRow.cells[j];
            if (rowName === "山名<山頂名>") {
                rowData["山名（ふりがな）"] = tableCell.querySelector("small").textContent.trim();
                rowData["山名"] = tableCell.querySelector("a").textContent.trim();
            } else {
                rowData[rowName] = tableCell.textContent.trim();
            }
        }
        data.push(rowData);
    }
    return data;
}

const table = dom.window.document.querySelector("table");
const json = tableToJson(table);
console.log(json);