oneClickSave (new version – September 2022)

function download(filename, text) {
  var tmp_node = document.createElement('a');
  tmp_node.setAttribute('href', 'data:text/plain;charset=utf-8,' + encodeURIComponent(text));
  tmp_node.setAttribute('download', filename);

  tmp_node.style.display = 'none';
  document.body.appendChild(tmp_node);

  tmp_node.click();

  document.body.removeChild(tmp_node);
}


function oneClickSave(include_title,comment) {
    download(
        ( document.title && include_title ? document.title + "." : "")
        + window.location.hostname
        + "."
        + ( comment != undefined  ? comment + "." : "" )
        // Avoiding colons for file system compatibilty and foregoing replaceAll() for browser compatibility.
        + new Date().toISOString().replace(":","-").replace(":","-")
        + ".DOM.html"
        // Generates the file name.

        , "<!-- Downloaded on " + new Date().toISOString() + " from " + document.location + " using oneClickSave. -->\n"
        // Notes the source URL and time stamp inside the file.

        + new XMLSerializer().serializeToString(document)
        // Similar to document.documentElement.outerHTML, but includes text outside <html></html>.
    );
}
oneClickSave(true);