create a blob and download it to local filesystem with user permission

by J. Jones

HTML

<div><input type="button" id="savetext" value="Save"/></div>
<textarea id="sometext">Hello World!</textarea>

CSS

#savetext {
  width: 40px;
}

JavaScript

function doSave(value, type) {
    var blob;
    if (typeof window.Blob == "function") {
        blob = new Blob([value], {type: type});
    } else {
        var BlobBuilder = window.BlobBuilder || window.MozBlobBuilder || window.WebKitBlobBuilder || window.MSBlobBuilder;
        var bb = new BlobBuilder();
        bb.append(value);
        blob = bb.getBlob(type);
    }
    var URL = window.URL || window.webkitURL;
    var bloburl = URL.createObjectURL(blob);
    location.href = bloburl;
}

var savebtn = document.getElementById("savetext"),
    textout = document.getElementById("sometext");
savebtn.onclick = function() {
    doSave(textout.value, "text/latex"); 
};