html - Download textarea contents as a file using only Javascript (no server-side)

Question

I am being asked to make a "download" button that downloads the contents of a textarea on the same page as a file, with the browser's "Save As..." dialog showing up. Copy/paste would do the job just fine, but it is a "requirement".

Right now, I am just posting the contents of the textarea to the server, which echos them back with Content-disposition: attachment slapped on. Is there a way to do this with just client-side Javascript?

Answer 1

This may be what you are looking for: http://thiscouldbebetter.wordpress.com/2012/12/18/loading-editing-and-saving-a-text-file-in-html5-using-javascrip/

It uses the browser's download dialogue, but supports only FF and Chrome, and maybe more browsers now?

---

   function saveTextAsFile(textToWrite, fileNameToSaveAs)
    {
    var textFileAsBlob = new Blob([textToWrite], {type:'text/plain'}); 
    var downloadLink = document.createElement("a");
    downloadLink.download = fileNameToSaveAs;
    downloadLink.innerHTML = "Download File";
    if (window.webkitURL != null)
    {
    // Chrome allows the link to be clicked
    // without actually adding it to the DOM.
    downloadLink.href = window.webkitURL.createObjectURL(textFileAsBlob);
    }
    else
    {
    // Firefox requires the link to be added to the DOM
    // before it can be clicked.
    downloadLink.href = window.URL.createObjectURL(textFileAsBlob);
    downloadLink.onclick = destroyClickedElement;
    downloadLink.style.display = "none";
    document.body.appendChild(downloadLink);
    }
    
    downloadLink.click();
    }

<textarea id=t>Hey</textarea><br>
<button onclick=saveTextAsFile(t.value,'download.txt')>Download</button>