Develop Reference

How to write data in JSON file in the EJS template file [duplicate]

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>

Convert _body content (string) to an arrayBuffer

I have an Ionic application which downloads a file from a Web API. The content of the file can be found in the _body property of the HTTP response.
What I'm trying to do is convert this text into an arrayBuffer so I can save the content into a file.
However, the issue that I'm having is that any file (PDF files in my instance) that have images and/or large in size either don't show up at all or show up as correputed files.
At first I thought this was an issue relating Ionic. So to make sure I tried to simulate this issue and I was able to reproduce it.
Is this snippet you can select a PDF file, then download it. You would find that the downloaded file is corrupted and exactly how my Ionic app displays them.
HTML:
<input type="file" id="file_input" class="foo" />
<div id="output_field" class="foo"></div>
JS:
$(document).ready(function(){
$('#file_input').on('change', function(e){
readFile(this.files[0], function(e) {
//manipulate with result...
$('#output_field').text(e.target.result);
try {
var file = new Blob([e.target.result], { type: 'application/pdf;base64' });
var fileURL = window.URL.createObjectURL(file);
var seconds = new Date().getTime() / 1000;
var fileName = "cert" + parseInt(seconds) + ".pdf";
var a = document.createElement("a");
document.body.appendChild(a);
a.style = "display: none";
a.href = fileURL;
a.download = fileName;
a.click();
}
catch (err){
$('#output_field').text(err);
}
});
});
});
function readFile(file, callback){
var reader = new FileReader();
reader.onload = callback
//reader.readAsArrayBuffer(file);
reader.readAsText(file);
}
https://jsfiddle.net/68qeau3h/3/
Now, when using reader.readAsArrayBuffer(file); everything works as expected, however in my particular case, I used reader.readAsText(file); because this is how the data is retrieve for me, this is text form.
When adding these lines of code to try to convert the string into an arrayBuffer
...
var buf = new ArrayBuffer(e.target.result.length * 2); // 2 bytes for each char
var bufView = new Uint16Array(buf);
for (var i=0, strLen=e.target.result.length; i<strLen; i++) {
bufView[i] = e.target.result.charCodeAt(i);
}
var file = new Blob([buf], { type: 'application/pdf' });
...
This will not work and generate PDF files that the browser can't open.
So to recap, what I'm trying to do is somehow convert the result I get from reader.readAsText(file); to what reader.readAsArrayBuffer(file); produces. Because the files I'm working with, or the data im retrieving from my backend is this text form.

Export 2D javascript array to Excel sheet

I know, there are hundreds of questions on this topic on here, but I still could not find satisfactory answers after a day of searching:
I have a 2D javascript array, which I want to download as an Excel sheet.
Here is a fiddle with the code I got so far:
https://jsfiddle.net/3an24jmw/7/
The download works, but there are several issues, which I could not solve after days of trying:
All items end up in the first column of the Excel sheet, because Excel interprets the "," separating the elements as part of the data. How can I separate the elements in a way Excel understands?
The file name is some cryptic code. How can I set the file name?
The downloaded file has a double .xls ending (.xls.xls). How can get a single .xls ending?
Excel tells me every time the file could be corrupted or unsafe. How do I prevent this?
Any help for any of these questions would be appreciated.
exportToCsv = function() {
var CsvString = "";
Results.forEach(function(RowItem, RowIndex) {
RowItem.forEach(function(ColItem, ColIndex) {
CsvString += ColItem + ',';
});
CsvString += "\r\n";
});
window.open('data:application/vnd.ms-excel,' + encodeURIComponent(CsvString));
}
UPDATE
I just found out by chance, that 1. 2. and 4. can be solved by replacing vnd.ms-excel with csv.
The file will not be .xls anymore, but the csv can be opened by Excel without problems and behaves like intended.
Only problem remaining is the file name!
UPDATE 2
Finally after 2 full workdays of searching and trying, I found the solution, which I would like to share here, to help anybody with the same problem:
Simply include an invisible <a> element, which defines the file an useful name using its download="somedata.csv" attribute.
Here is my final and fully functional fiddle:
https://jsfiddle.net/3an24jmw/25/

Finaly after 2 full workdays of searching and trying, I found the solution, which I would like to share here, to help anybody with the same problem:
Simply include an invisible element, which gives the file an usefull name using its download="somedata.csv" attribute:
Here is my final and fully functional fiddle:
https://jsfiddle.net/3an24jmw/25/
var Results = [
["Col1", "Col2", "Col3", "Col4"],
["Data", 50, 100, 500],
["Data", -100, 20, 100],
];
exportToCsv = function() {
var CsvString = "";
Results.forEach(function(RowItem, RowIndex) {
RowItem.forEach(function(ColItem, ColIndex) {
CsvString += ColItem + ',';
});
CsvString += "\r\n";
});
CsvString = "data:application/csv," + encodeURIComponent(CsvString);
var x = document.createElement("A");
x.setAttribute("href", CsvString );
x.setAttribute("download","somedata.csv");
document.body.appendChild(x);
x.click();
}

The separator Excel expects for csv depends on your system locale setting for list separator.
You can hint Excel which separator to use for your csv file by adding "sep=," as the first line.
In your case use could use: var CsvString = '"sep=,"\r\n';

https://github.com/shuchkin/simplexlsxgen#js-array-to-excel-ajax
<?php // array2excel.php
if (isset($_POST['array2excel'])) {
require __DIR__.'/simplexlsxgen/src/SimpleXLSXGen.php';
$data = json_decode($_POST['array2excel'], false);
\Shuchkin\SimpleXLSXGen::fromArray($data)->downloadAs('file.xlsx');
return;
}
?>
<html lang="en">
<head>
<title>JS array to Excel</title>
</head>
<script>
function array2excel() {
var books = [
["ISBN", "title", "author", "publisher", "ctry"],
[618260307, "The Hobbit", "J. R. R. Tolkien", "Houghton Mifflin", "USA"],
[908606664, "Slinky Malinki", "Lynley Dodd", "Mallinson Rendel", "NZ"]
];
var json = JSON.stringify(books);
var request = new XMLHttpRequest();
request.onload = function () {
if (this.status === 200) {
var file = new Blob([this.response], {type: this.getResponseHeader('Content-Type')});
var fileURL = URL.createObjectURL(file);
var filename = "", m;
var disposition = this.getResponseHeader('Content-Disposition');
if (disposition && (m = /"([^"]+)"/.exec(disposition)) !== null) {
filename = m[1];
}
var a = document.createElement("a");
if (typeof a.download === 'undefined') {
window.location = fileURL;
} else {
a.href = fileURL;
a.download = filename;
document.body.appendChild(a);
a.click();
}
} else {
alert("Error: " + this.status + " " + this.statusText);
}
}
request.open('POST', "array2excel.php");
request.responseType = "blob";
request.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
request.send("array2excel=" + encodeURIComponent(json));
}
</script>
<body>
<input type="button" onclick="array2excel()" value="array2excel" />
</body>
</html>

How to support "\n" when exporting csv file with javascript

I am trying to export an array data to a csv file, which works fine unless it has break line("\n"). I hope to make it support break line in a single cell, is it possible?
I tried replace \n into "\n" or "'\n'" but it does not work
The function I am using:
function arrayToCSVConvertor(arrData, ReportTitle) {
var CSV='';
arrData.forEach(function(infoArray, index){
var dataString = infoArray.join(",");
//dataString= dataString.split('\n').join('\\n');//Here, need something to suport "\n"
CSV += dataString+ "\n";
});
if (CSV == '') {
alert("Invalid data");
return;
}
//create a link and click then remove
var link = document.createElement("a");
link.id="lnkDwnldLnk";
//this part will append the anchor tag and remove it after automatic click
document.body.appendChild(link);
var csv = CSV;
/* window.open(encodeURI(csv));*/
var blob = new Blob([csv], { type: 'text/csv' });
//var csvUrl = window.webkitURL.createObjectURL(blob);
var csvUrl = createObjectURL(blob);
var filename = ReportTitle+'.csv';
if(navigator.msSaveBlob){//IE 10
return navigator.msSaveBlob(blob, filename);
}else{
$("#lnkDwnldLnk")
.attr({
'download': filename,
'href': csvUrl
});
$('#lnkDwnldLnk')[0].click();
document.body.removeChild(link);
}
}
PS: I have Chinese words inside the array

I suggest avoiding the pain of working with CSV directly and all it's little variants and just use some library like Papa Parse to handle the job for you.
Basically, the new line to be used within a value should be a \n and the new line to end a record should be \r\n but as #user2864740 commented the results vary based on the encoding of the file and where you are going to open it.

Convert a base64 to a file in Javascript

The goal is to transform a base64 string into a sendable jpg file, I cant use the html input type file but i have to serve in the same format. I am bit lost with file generation. (I am on a client side mobile app).
This is what i have:
file = "data:image/jpg;base64,#{imageData}"
imageData is the base64 string
There is a way to transform this into a valid file?

Disclaimer: Produces an invalid result (close, but invalid)
I've done the reverse earlier last week - that is, load an image as binary data (to get around the requirement to run file from localhost).
In it, I:
loaded the file
base64 converted it
added a pre-amble to the base64 string
set the constructed string to be the src of an img element
This worked just fine. Upon reading your question, I tried to simply reverse the process. I was however, unsuccessfull somewhere. The data is extracted from the image correctly, then somewhere afterwards (I think in the call to atob that un-encodes it) the data is messed-up.
The saved files are an unexpected size, have an added char before "%PNG" and have some missing data in the middle of the file. I'm rather perplexed at this point, to be honest.
Anyhow, here's the code I've tried:
1. Code to read a file and stuff the data into an element
// fileVar is an object as returned by <input type='file'>
// imgElem is an <img> element - (doesn't need to be added to the DOM)
function loadImgFromFile(fileVar, imgElem)
{
var fileReader = new FileReader();
fileReader.onload = onFileLoaded;
fileReader.readAsBinaryString(fileVar);
function onFileLoaded(fileLoadedEvent)
{
var result,data;
data = fileLoadedEvent.target.result;
result = "data:";
result += fileVar.type;
result += ";base64,";
result += btoa(data);
imgElem.src = result;
}
}
2. Attempt to grab data from an image/canvas and force the download of it using a programmer-supplied filename.
<!doctype html>
<html>
<head>
<script>
function byId(e){return document.getElementById(e)}
function newEl(tag){return document.createElement(tag)}
window.addEventListener('load', onPageLoaded, false);
function onPageLoaded(evt)
{
var imgElem = byId('srcImg');
imgElem.onload = function(){saveImgAsFile( byId('srcImg'), "myImage.png" );};
// simple result of canvas.toDataURL() called on a 5x5 pixel image of a '+'
imgElem.src = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHklEQVQIW2NkQID/QCYjiAsmoABFEMRBAThVYmgHAAhoBQWHhfyYAAAAAElFTkSuQmCC";
// use the below line instead of the one above, if you wish to assign an actual image file, rather than the result of call to canvas.toDataURL()
// the base64 string allows me to keep it all in the one file, also, to run if opened via a double-click, rather than having to run from localhost
// imgElem.src = "img/1x1.png";
}
function saveImgAsFile(imgElem, fileName)
{
// get a base64 encoded string from an image element
var srcElem = imgElem;
var dstCanvas = newEl('canvas');
dstCanvas.width = srcElem.naturalWidth;
dstCanvas.height = srcElem.naturalHeight;
var ctx = dstCanvas.getContext('2d');
ctx.drawImage(srcElem,0,0);
var imgSrcStr = dstCanvas.toDataURL();
// extract the image type
var colonPos = imgSrcStr.indexOf(":");
var semiColonPos = imgSrcStr.indexOf(";");
var imgType = imgSrcStr.slice(colonPos+1, semiColonPos);
console.log("image type: " + imgType);
// extract the image data
var commaPos = imgSrcStr.indexOf(',');
var base64ImgString = imgSrcStr.slice(commaPos + 1);
console.log("Data: " + base64ImgString);
// holds the data that is actually written to disk for this image
//** I think the error occurs during this step **//
var unencodedImage = atob(base64ImgString);
var imgFileAsBlob = new Blob( [unencodedImage], {type: imgType} );
var fileNameToUse = fileName;
var downloadLink = newEl('a');
downloadLink.download = fileNameToUse;
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(imgFileAsBlob);
}
else
{
// Firefox requires the link to be added to the DOM
// before it can be clicked.
downloadLink.href = window.URL.createObjectURL(imgFileAsBlob);
downloadLink.onclick = destroyClickedElement;
downloadLink.style.display = "none";
document.body.appendChild(downloadLink);
}
downloadLink.click();
}
/*
function saveTextAsFile()
{
var textToWrite = "This is just some random content";
var textFileAsBlob = new Blob([textToWrite], {type:'text/plain'})
var fileNameToSaveAs = "myFile.txt";
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();
}
*/
function destroyClickedElement(event)
{
document.body.removeChild(event.target);
}
</script>
</head>
<body>
<img id='srcImg'/>
</body>
</html>