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>

HTML Editor with Download Option

I'm looking for a way to add a download feature to my JS that will create a file using the programming that a user might enter in, lets say, a <textarea>. Are there any features in JS that would work similar to this? (HTML Format!!)
var x = document.write("<p>Hi!</p>");
window.replace(x);
And then:
<button onclick="open()">Save</button>
<script>
var hi = document.write("<p>hi</p>;");
open() {
window.open(hi)
}
</script>
After they opened the variable on the new page, the user could use ctrl + s to save the page displayed. Ideas?
Thanks in advance.

<textarea id="text-val" rows="4" style="height: 80%;width: 90%;"></textarea><br/><br/>
<input type="button" id="dwn-btn" value="Save" />
<script>
function download(filename, text) {
var element = document.createElement('a');
element.setAttribute('href', 'data:text/plain;charset=utf-8,' + encodeURIComponent(text));
element.setAttribute('download', filename);
element.style.display = 'none';
document.body.appendChild(element);
element.click();
document.body.removeChild(element);
}
document.getElementById("dwn-btn").addEventListener("click", function() {
var text = document.getElementById("text-val").value;
var filename = "example.html";
download(filename, text);
}, false);
</script>
I hope this is what you are expecting

Create new Blob from your html script with application/octet-stream mime type. Then use URL.createOjectURL api to generate download link. And navigate to that link. In this example code I navigated using creating temporary link (<a>) element.
function download() {
var blobPart = ['<h1>Test</h1>'];
var blob = new Blob(blobPart, {
type: "application/octet-stream"
});
var urlObj = URL.createObjectURL(blob);
var a = document.createElement('a');
document.body.appendChild(a);
a.href = urlObj;
a.download = 'filename.html';
a.click();
a.remove();
}
document.getElementById('download-btn').addEventListener('click', download);
Download

Client side Javascript get video width/height before upload

I've been trying to piece together a combination of HTML5 video tag + the FileReader API but I haven't figured out how to get the dimensions of a video that a user is providing from their own computer.
Here is what I am referencing for width/ height:
HTML5 Video Dimensions
<video id="foo" src="foo.mp4"></video>
var vid = document.getElementById("foo");
vid.videoHeight; // returns the intrinsic height of the video
vid.videoWidth; // returns the intrinsic width of the video
But I want to know if it's possible to do this with a file from a user's computer (that they have selected via a normal input html tag).
Thanks!

A bit unclean solution using basic FileReader + Data URL.
<html>
<head>
<style>
div {
margin: 20px;
}
</style>
</head>
<body>
<h1>Get Dimensions</h1>
<div>
<label for="load-file">Load a file:</label>
<input type="file" id="load-file">
</div>
<div>
<button type="button" id="done-button">Get me dimensions</button>
</div>
<script src="//cdn.jsdelivr.net/jquery/2.1.4/jquery.js"></script>
<script>
(function ($) {
$('#done-button').on('click', function () {
var file = $('#load-file')[0].files[0];
var reader = new FileReader();
var fileType = file.type;
console.log("type", fileType);
reader.addEventListener("load", function () {
var dataUrl = reader.result;
var videoId = "videoMain";
var $videoEl = $('<video id="' + videoId + '"></video>');
$("body").append($videoEl);
$videoEl.attr('src', dataUrl);
var videoTagRef = $videoEl[0];
videoTagRef.addEventListener('loadedmetadata', function(e){
console.log(videoTagRef.videoWidth, videoTagRef.videoHeight);
});
}, false);
if (file) {
reader.readAsDataURL(file);
}
});
})(jQuery);
</script>
</body>
</html>

Here is a simple and fast solution to get a video's size before upload.
It doesn't require any dependency.
const url = URL.createObjectURL(file);
const $video = document.createElement("video");
$video.src = url;
$video.addEventListener("loadedmetadata", function () {
console.log("width:", this.videoWidth);
console.log("height:", this.videoHeight);
});

const onSelectVideo = (files) => {
const file = files[0];
const url = URL.createObjectURL(file);
let videoId = "videoMain";
const video = document.createElement("video");
const body = document.getElementsByTagName("body");
video.setAttribute("src", url);
video.setAttribute("videoId", videoId);
body[0]?.append(video);
let videoTagRef = document.querySelector("[videoId='videoMain']");
videoTagRef.addEventListener("loadedmetadata", function (e) {
console.log(videoTagRef.videoWidth, videoTagRef.videoHeight);
});}

Downloading or rendering on an Iframe depending on app Logic in Angular JS

I have an angular JS app on which I download a pdf file and then create a blob from it. Like this:
vm.fileData = new ApiDownloadFile({fileId: 1});
return vm.fileData.$query()
.then(function(response) {
try{
console.log("Try..." + new Date());
$log.log(response);
var arrayBufferView = new Uint8Array(response.Body.data);
$log.log(arrayBufferView);
var file = new Blob( [arrayBufferView], {type: response.ContentType});
var link = document.createElement('a');
link.href = window.URL.createObjectURL(file);
link.download = response.fileName;
link.click();
console.log("After..." + new Date());
console.log("GENERATED LINK: "+link.href);
//PDFObject.embed(link.href, "#my-container");
}
catch(e) {
console.log("Execption...");
// TypeError old chrome and FF
window.BlobBuilder = window.BlobBuilder ||
window.WebKitBlobBuilder ||
window.MozBlobBuilder ||
window.MSBlobBuilder;
if (e.name == 'TypeError' && window.BlobBuilder) {
var bb = new BlobBuilder();
bb.append(response.Body.data);
var file = bb.getBlob("image/jpeg");
var link = document.createElement('a');
link.href = window.URL.createObjectURL(file);
link.download = "1.jpg";
//link.click();
}
else if (e.name == "InvalidStateError") {
// InvalidStateError (tested on FF13 WinXP)
var jpeg = new Blob(response.Body.data, {type: "image/jpeg"});
}
else {
// We're screwed, blob constructor unsupported entirely
}
}
},function(err) {
$log.log(err);
});
};
I can donwload the file easily by creating an 'a' element and then clicking it. However I would like to be able to either download it on the browser or render it on an Iframe I have in my view. The logic should be something like this:
if download == true:
create the <a> element and click it to download file.
else:
render the pdf on an iframe and don´t download on browser.
However I´m not able to get the blob URL to be rendered on the Iframe. I´m using PDFObject to visualize the PDF. Can anyone help me achieve this?

Do this in your page
<iframe ng-if="IframeManager.Url" ng-src="{{ IframeManager.Url }}"></iframe>
Then in your controller add
$scope.Download = true;
$scope.IframeManager = {
Show: function (url) {
$scope.IframeManager.Url = url;
},
Hide: function () {
$scope.IframeManager.Url = null;
}
};
So if you want to show the file you do your preview routine blob conversion and get the url
if ($scope.Download) {
var link = document.createElement('a');
link.href = window.URL.createObjectURL(file);
link.download = response.fileName;
link.click();
console.log("After..." + new Date());
console.log("GENERATED LINK: "+link.href);
} else {
$scope.IframeManager.Show(window.URL.createObjectURL(file));
}

How to read file content in a javascript variable?

I got a small script to split the text inside 'var foo' after every 4 characters. It is working fine.
but my actual data is in a text file say 'a.txt'. How do I take this entire file text in 'var foo'. and write the split output to another text file?
var foo = "this is sample text !!!";
var arr = [];
for (var i = 0; i < foo.length; i++) {
if (i % 4 == 0 && i != 0)
arr.push(foo.substring(i - 4, i));
if (i == foo.length - 1)
arr.push(foo.substring(i - (i % 4), i+1));
}
document.write(arr);
console.log(arr);

To get the content of the file you need to select a file using an input tag.
<!DOCTYPE html>
<head>
<meta charset="UTF-8">
</head>
<body>
<input id="input" type="file" accept="text/plain">
<script src="script.js"></script>
</body>
A good moment to read the content of the file is in the change event.
const input = document.querySelector("#input");
input.addEventListener("change", () => {
const file = input.files.item(0);
});
To read the content of the file as a string you need to convert it.
function fileToText(file, callback) {
const reader = new FileReader();
reader.readAsText(file);
reader.onload = () => {
callback(reader.result);
};
}
The content of the file as a string will be available to the the callback function. You can create a link and use the click event to download the string into a text file.
function save(content, fileName, mime) {
const blob = new Blob([content], {
tipe: mime
});
const url = URL.createObjectURL(blob);
const a = document.createElement("a");
a.href = url;
a.download = fileName;
a.click();
}
Here is the complete code
const input = document.querySelector("#input");
input.addEventListener("change", () => {
const file = input.files.item(0);
fileToText(file, (text) => {
save(text, "fileName.txt", "text/plain");
});
});
function fileToText(file, callback) {
const reader = new FileReader();
reader.readAsText(file);
reader.onload = () => {
callback(reader.result);
};
}
function save(content, fileName, mime) {
const blob = new Blob([content], {
tipe: mime
});
const url = URL.createObjectURL(blob);
const a = document.createElement("a");
a.href = url;
a.download = fileName;
a.click();
}
<!DOCTYPE html>
<head>
<meta charset="UTF-8">
</head>
<body>
<input id="input" type="file" accept="text/plain">
<script src="script.js"></script>
</body>
You can read more about manipulating files in JavaScript here: https://www.html5rocks.com/en/tutorials/file/dndfiles/

Solution to this helped me :
How do I load the contents of a text file into a javascript variable?
var client = new XMLHttpRequest();
client.open('GET', '/foo.txt');
client.onreadystatechange = function() {
alert(client.responseText);
}
client.send();