JSFiddle - React, Tailwind, and code Playground

HTML

<button type="button" onclick="div2html()">Save HTML</button>
<br><br>
<div style="border: 1px solid">
    <div id="div2save">
        <p class="bigbold">bla<p>
    </div>
</div>

CSS

.bigbold {
    font-weight: bold;
    font-size: 20px;
}

JavaScript

function div2html() {
    var inner=document.getElementById("div2save").innerHTML;
    var html="<html><head></head><body>"+inner+"</body></html>";
    saveTextAsFile("div2html.html", html);
}


function saveTextAsFile(fileNameToSaveAs, textToWrite) {  
  var ie = navigator.userAgent.match(/MSIE\s([\d.]+)/),
      ie11 = navigator.userAgent.match(/Trident\/7.0/) && navigator.userAgent.match(/rv:11/),
      ieEDGE = navigator.userAgent.match(/Edge/g),
      ieVer=(ie ? ie[1] : (ie11 ? 11 : (ieEDGE ? 12 : -1)));

  if (ie && ieVer<10) {
    console.log("No blobs on IE ver<10");
    return;
  }

  var textFileAsBlob = new Blob([textToWrite], {
    type: 'text/plain'
  });

  if (ieVer>-1) {
    window.navigator.msSaveBlob(textFileAsBlob, fileNameToSaveAs);

  } else {
    var downloadLink = document.createElement("a");
    downloadLink.download = fileNameToSaveAs;
    downloadLink.href = window.URL.createObjectURL(textFileAsBlob);
    downloadLink.onclick = function(e) { document.body.removeChild(e.target); };
    downloadLink.style.display = "none";
    document.body.appendChild(downloadLink);
    downloadLink.click();
  }
}