I want to Write Data to existing file using JavaScript.
I don't want to print it on console.
I want to Actually Write data to abc.txt.
I read many answered question but every where they are printing on console.
at some place they have given code but its not working.
So please can any one help me How to actually write data to File.
I referred the code but its not working:
its giving error:
Uncaught TypeError: Illegal constructor
on chrome and
SecurityError: The operation is insecure.
on Mozilla
var f = "sometextfile.txt";
writeTextFile(f, "Spoon")
writeTextFile(f, "Cheese monkey")
writeTextFile(f, "Onion")
function writeTextFile(afilename, output)
{
var txtFile =new File(afilename);
txtFile.writeln(output);
txtFile.close();
}
So can we actually write data to file using only Javascript or NOT?
You can create files in browser using Blob and URL.createObjectURL. All recent browsers support this.
You can not directly save the file you create, since that would cause massive security problems, but you can provide it as a download link for the user. You can suggest a file name via the download attribute of the link, in browsers that support the download attribute. As with any other download, the user downloading the file will have the final say on the file name though.
var textFile = null,
makeTextFile = function (text) {
var data = new Blob([text], {type: 'text/plain'});
// If we are replacing a previously generated file we need to
// manually revoke the object URL to avoid memory leaks.
if (textFile !== null) {
window.URL.revokeObjectURL(textFile);
}
textFile = window.URL.createObjectURL(data);
// returns a URL you can use as a href
return textFile;
};
Here's an example that uses this technique to save arbitrary text from a textarea.
If you want to immediately initiate the download instead of requiring the user to click on a link, you can use mouse events to simulate a mouse click on the link as Lifecube's answer did. I've created an updated example that uses this technique.
var create = document.getElementById('create'),
textbox = document.getElementById('textbox');
create.addEventListener('click', function () {
var link = document.createElement('a');
link.setAttribute('download', 'info.txt');
link.href = makeTextFile(textbox.value);
document.body.appendChild(link);
// wait for the link to be added to the document
window.requestAnimationFrame(function () {
var event = new MouseEvent('click');
link.dispatchEvent(event);
document.body.removeChild(link);
});
}, false);
Some suggestions for this -
If you are trying to write a file on client machine, You can't do this in any cross-browser way. IE does have methods to enable "trusted" applications to use ActiveX objects to read/write file.
If you are trying to save it on your server then simply pass on the text data to your server and execute the file writing code using some server side language.
To store some information on the client side that is considerably small, you can go for cookies.
Using the HTML5 API for Local Storage.
If you are talking about browser javascript, you can not write data directly to local file for security reason. HTML 5 new API can only allow you to read files.
But if you want to write data, and enable user to download as a file to local. the following code works:
function download(strData, strFileName, strMimeType) {
var D = document,
A = arguments,
a = D.createElement("a"),
d = A[0],
n = A[1],
t = A[2] || "text/plain";
//build download link:
a.href = "data:" + strMimeType + "charset=utf-8," + escape(strData);
if (window.MSBlobBuilder) { // IE10
var bb = new MSBlobBuilder();
bb.append(strData);
return navigator.msSaveBlob(bb, strFileName);
} /* end if(window.MSBlobBuilder) */
if ('download' in a) { //FF20, CH19
a.setAttribute("download", n);
a.innerHTML = "downloading...";
D.body.appendChild(a);
setTimeout(function() {
var e = D.createEvent("MouseEvents");
e.initMouseEvent("click", true, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);
a.dispatchEvent(e);
D.body.removeChild(a);
}, 66);
return true;
}; /* end if('download' in a) */
//do iframe dataURL download: (older W3)
var f = D.createElement("iframe");
D.body.appendChild(f);
f.src = "data:" + (A[2] ? A[2] : "application/octet-stream") + (window.btoa ? ";base64" : "") + "," + (window.btoa ? window.btoa : escape)(strData);
setTimeout(function() {
D.body.removeChild(f);
}, 333);
return true;
}
to use it:
download('the content of the file', 'filename.txt', 'text/plain');
Try
let a = document.createElement('a');
a.href = "data:application/octet-stream,"+encodeURIComponent("My DATA");
a.download = 'abc.txt';
a.click();
If you want to download binary data look here
Update
2020.06.14 I upgrade Chrome to 83.0 and above SO snippet stop works (reason: sandbox security restrictions) - but JSFiddle version works - here
Above answer is useful but, I found code which helps you to download text file directly on button click.
In this code you can also change filename as you wish. It's pure javascript function with HTML5.
Works for me!
function saveTextAsFile()
{
var textToWrite = document.getElementById("inputTextToSave").value;
var textFileAsBlob = new Blob([textToWrite], {type:'text/plain'});
var fileNameToSaveAs = document.getElementById("inputFileNameToSaveAs").value;
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();
}
const data = {name: 'Ronn', age: 27}; //sample json
const a = document.createElement('a');
const blob = new Blob([JSON.stringify(data)]);
a.href = URL.createObjectURL(blob);
a.download = 'sample-profile'; //filename to download
a.click();
Check Blob documentation here - Blob MDN to provide extra parameters for file type. By default it will make .txt file
In the case it is not possibile to use the new Blob solution, that is for sure the best solution in modern browser, it is still possible to use this simpler approach, that has a limit in the file size by the way:
function download() {
var fileContents=JSON.stringify(jsonObject, null, 2);
var fileName= "data.json";
var pp = document.createElement('a');
pp.setAttribute('href', 'data:text/plain;charset=utf-8,' + encodeURIComponent(fileContents));
pp.setAttribute('download', fileName);
pp.click();
}
setTimeout(function() {download()}, 500);
$('#download').on("click", function() {
function download() {
var jsonObject = {
"name": "John",
"age": 31,
"city": "New York"
};
var fileContents = JSON.stringify(jsonObject, null, 2);
var fileName = "data.json";
var pp = document.createElement('a');
pp.setAttribute('href', 'data:text/plain;charset=utf-8,' + encodeURIComponent(fileContents));
pp.setAttribute('download', fileName);
pp.click();
}
setTimeout(function() {
download()
}, 500);
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<button id="download">Download me</button>
Use the code by the user #useless-code above (https://stackoverflow.com/a/21016088/327386) to generate the file.
If you want to download the file automatically, pass the textFile that was just generated to this function:
var downloadFile = function downloadURL(url) {
var hiddenIFrameID = 'hiddenDownloader',
iframe = document.getElementById(hiddenIFrameID);
if (iframe === null) {
iframe = document.createElement('iframe');
iframe.id = hiddenIFrameID;
iframe.style.display = 'none';
document.body.appendChild(iframe);
}
iframe.src = url;
}
I found good answers here, but also found a simpler way.
The button to create the blob and the download link can be combined in one link, as the link element can have an onclick attribute. (The reverse seems not possible, adding a href to a button does not work.)
You can style the link as a button using bootstrap, which is still pure javascript, except for styling.
Combining the button and the download link also reduces code, as fewer of those ugly getElementById calls are needed.
This example needs only one button click to create the text-blob and download it:
<a id="a_btn_writetofile" download="info.txt" href="#" class="btn btn-primary"
onclick="exportFile('This is some dummy data.\nAnd some more dummy data.\n', 'a_btn_writetofile')"
>
Write To File
</a>
<script>
// URL pointing to the Blob with the file contents
var objUrl = null;
// create the blob with file content, and attach the URL to the downloadlink;
// NB: link must have the download attribute
// this method can go to your library
function exportFile(fileContent, downloadLinkId) {
// revoke the old object URL to avoid memory leaks.
if (objUrl !== null) {
window.URL.revokeObjectURL(objUrl);
}
// create the object that contains the file data and that can be referred to with a URL
var data = new Blob([fileContent], { type: 'text/plain' });
objUrl = window.URL.createObjectURL(data);
// attach the object to the download link (styled as button)
var downloadLinkButton = document.getElementById(downloadLinkId);
downloadLinkButton.href = objUrl;
};
</script>
Here is a single-page local-file version for use when you need the extra processing functionality of a scripting language.
Save the code below to a text file
Change the file extension from '.txt' to '.html'
Right-click > Open With... > notepad
Program word processing as needed, then save
Double-click html file to open in default browser
Result will be previewed in the black box, click download to get the resulting text file
Code:
<!DOCTYPE HTML>
<HTML>
<HEAD>
</HEAD>
<BODY>
<SCRIPT>
// do text manipulation here
let string1 = 'test\r\n';
let string2 = 'export.';
// assemble final string
const finalText = string1 + string2;
// convert to blob
const data = new Blob([finalText], {type: 'text/plain'});
// create file link
const link = document.createElement('a');
link.innerHTML = 'download';
link.setAttribute('download', 'data.txt');
link.href = window.URL.createObjectURL(data);
document.body.appendChild(link);
// preview the output in a paragraph
const htmlBreak = string => {
return string.replace(/(?:\r\n|\r|\n)/g, '<br>');
}
const preview = document.createElement('p');
preview.innerHTML = htmlBreak(finalText);
preview.style.border = "1px solid black";
document.body.appendChild(preview);
</SCRIPT>
</BODY>
</HTML>
I have this code:
$.post('/pdf/render', params, function (data) {
var blob = new Blob([data], {type: 'application/pdf'});
var downloadUrl = URL.createObjectURL(blob);
var a = document.createElement("a");
a.href = downloadUrl;
a.download = "results.pdf";
document.body.appendChild(a);
a.click();
}):
Once my PDF downloads, the clicked URL and blob saves my PDF with the correcct number of pages, but there is nothing in the PDF. Am I doing something wrong with my blob? Why would there be no content when I am getting the content from the backend?
For clairfication, I checked with cURL and got a proper PDF with content.
I am having trouble exporting the contents of a div into a .docx file. I am using FileSaver.js which can be found here: https://github.com/eligrey/FileSaver.js/.
My JavaScript Function:
function exportNote(){
var blob = new Blob([document.getElementById('editor').innerHTML], {
type: "application/vnd.openxmlformats-officedocument.wordprocessingml.document;charset=utf-8"
});
saveAs(blob, "note.docx");
}
I get a download that appears to be a word file but when I open it I get the following error:
The Open XML file note.docx cannot be opened because
there are problems with the contents or the file name
might contain invalid characters (for example. /).
Details:
The file is corrupt and cannot be opened.
For graphical purposes:
The text area is the area I am trying to export into a word document which is under <div id="editor"></div>.
jsfiddle
Html
<div id="main">
this is content of div
</div>
JavaScript
function downloadInnerHtml(filename, elId) {
var elHtml = document.getElementById(elId).innerHTML;
var link = document.createElement('a');
link.setAttribute('download', filename);
link.setAttribute('href', 'data:' + 'text/doc' + ';charset=utf-8,' + encodeURIComponent(elHtml));
link.click();
}
var fileName = 'tags.doc'; // You can use the .txt extension if you want
downloadInnerHtml(fileName, 'main');
There is another solution to this problem using an open source library on github under the MIT license: https://github.com/evidenceprime/html-docx-js.
My solution:
function exportNote(contentId){
var filename = 'note.html'
var htmlDoc = document.getElementById(contentId).innerHTML;
var converted = htmlDocx.asBlob(htmlDoc);
saveAs(converted, "notes.docx");
}
Since somebody had a problem in the comments, I'm pasting in what I am actively using. The function I pasted here is darn near verbatim from this site: https://www.codexworld.com/export-html-to-word-doc-docx-using-javascript/
So credit to them. The key to this is that saving the contents of a div to a file is not a proper HTML document, and that causes Word to balk. It needs a BODY, HTML and some of that xmlns attributing. This function gets the innerHtml and wraps it with that, before doing the actual save.
Simply call Export2Word() with the name of the element that holds the content you want to save and the filename:
Export2Word('divMyContent','MyFileNameWithoutExtension');
function Export2Word(element, filename = ''){
var preHtml = "<html xmlns:o='urn:schemas-microsoft-com:office:office' xmlns:w='urn:schemas-microsoft-com:office:word' xmlns='http://www.w3.org/TR/REC-html40'><head><meta charset='utf-8'><title>Export HTML To Doc</title></head><body>";
var postHtml = "</body></html>";
var content = document.getElementById(element).innerHTML;
var html = preHtml+content+postHtml;
var blob = new Blob(['\ufeff', html], {
type: 'application/msword'
});
// Specify link url
var url = 'data:application/vnd.ms-word;charset=utf-8,' + encodeURIComponent(html);
// Specify file name
filename = filename?filename+'.docx':'document.docx';
// Create download link element
var downloadLink = document.createElement("a");
document.body.appendChild(downloadLink);
if(navigator.msSaveOrOpenBlob ){
navigator.msSaveOrOpenBlob(blob, filename);
}else{
// Create a link to the file
downloadLink.href = url;
// Setting the file name
downloadLink.download = filename;
//triggering the function
downloadLink.click();
}
document.body.removeChild(downloadLink);
}
I have a BLOB URL, and I want to recreate it as a second BLOB URL, so that it is downloaded by default.
var blob1 = new Blob(["Hello world!"], { type: "text/plain" });
url1 = window.URL.createObjectURL(blob1);
blob2=new Blob([url1], {type: 'application/octet-stream'});
url2 = window.URL.createObjectURL(blob2);
var a = document.createElement("a");
document.body.appendChild(a);
a.style = "display: none";
a.href = url2;
a.click();
window.URL.revokeObjectURL(url);
See in JSFiddle:
https://jsfiddle.net/7spry3jn/
But this only creates a text file containint the first URL. How can I Read data from the first BLOB URL in Javascript and feed it to create the second BLOB?
You can use the download attr in anchor element, that force the download and you dont need to reate another blob.
But you need to pay attentio about browser support, see here all the browsers that accept the downloadattr: Can I Use
var blob1 = new Blob(["Hello world!"], { type: "text/plain" });
url = window.URL.createObjectURL(blob1);
var a = document.createElement("a");
document.body.appendChild(a);
a.style = "display: none";
a.href = url;
a.setAttribute("download","Any name");
a.click();
window.URL.revokeObjectURL(url);
And to read the content from a Blob you can use FileReader like this:
var myBlob = new Blob(["Hello"], {type : "text/plain"});
var myReader = new FileReader();
//handler executed once reading(blob content referenced to a variable) from blob is finished.
myReader.addEventListener("loadend", function(e){
document.getElementById("text").innerHTML = e.srcElement.result;//prints a string
});
//start the reading process.
myReader.readAsText(myBlob);
<p id="text"></p>
Following Problem: this Code isn't working in IE9. And in an actual Chrome Browser it is working but the downloaded file is corrupt (the "corrupted file" part also could happen elsewhere ... any suggestion how to do it in IE9 would be nice ).
var file = records[0].data.Files[0].Value.Buffer;
var fileName = records[0].data.Files[0].Value.FileName;
var a = window.document.createElement('a');
a.href = window.URL.createObjectURL(new Blob([file], { type: 'application/octet-stream' }));
a.download = fileName;
document.body.appendChild(a)
a.click();
document.body.removeChild(a)