Gravar conteudo de textarea num ficheiro

function saveTextAsFile()
{        
    var textToWrite = document.getElementById("inputTextToSave").value;
    var textFileAsBlob = new Blob([textToWrite], {type:'text/plain'});
    var fileNameToSaveAs = "nome_ficheiro.txt";
   
    var downloadLink = document.createElement("a");
    downloadLink.download = fileNameToSaveAs;
    downloadLink.innerHTML = "link";
   
    window.URL = window.URL || window.webkitURL;
                 
    downloadLink.href = window.URL.createObjectURL(textFileAsBlob);
    downloadLink.onclick = destroyClickedElement;
    downloadLink.style.display = "none";
    document.body.appendChild(downloadLink);
   
    downloadLink.click();
}
function destroyClickedElement(event)
{
    document.body.removeChild(event.target);
}