Javascript - File saved to disk is stuck in Chrome's memory - javascript

I have this code:
function saveFile(str, part) {
var textFileAsBlob = new Blob([str], {type:"text/plain"});
var fileNameToSaveAs = "Parsed audio - part "+part;
var downloadLink = document.createElement("a");
downloadLink.download = fileNameToSaveAs;
downloadLink.innerHTML = "Download File";
if (window.URL != null)
{
// Chrome allows the link to be clicked
// without actually adding it to the DOM.
downloadLink.href = window.URL.createObjectURL(textFileAsBlob);
}
downloadLink.click();
}
It works okay, except this one problem with Chrome: The blob's "footprint" or whatever is kept in Chrome's main process' memory. When download window is opened, the whole blob (250MB in my case!) is copied into main process' memory. That's kinda bad since if I save multiple files, I eventually fill memory up to 750MB, and at that point chrome stops downloading files with "Not found" error. Pic: http://i.stack.imgur.com/j5PUn.jpg
Am I doing some stupid mistake or is this Chrome's fault? Can I clean Chrome's memory to get rid of this problem?

As my comment seemed to be the answer you were looking for, I've put it as an actual answer
You're not releasing the blob URL after the click, which means the GC can't get rid of the blob
// after the click
URL.revokeObjectURL(downloadLink.href);

Related

JavaScript: How to create and save text file [duplicate]

This question already has answers here:
How to create a file in memory for user to download, but not through server?
(22 answers)
Closed 2 years ago.
I have data that I want to write to a file, and open a file dialog for the user to choose where to save the file. It would be great if it worked in all browsers, but it has to work in Chrome. I want to do this all client-side.
Basically I want to know what to put in this function:
saveFile: function(data)
{
}
Where the function takes in data, has the user select a location to save the file, and creates a file in that location with that data.
Using HTML is fine too, if that helps.
A very minor improvement of the code by Awesomeness01 (no need for anchor tag) with addition as suggested by trueimage (support for IE):
// Function to download data to a file
function download(data, filename, type) {
var file = new Blob([data], {type: type});
if (window.navigator.msSaveOrOpenBlob) // IE10+
window.navigator.msSaveOrOpenBlob(file, filename);
else { // Others
var a = document.createElement("a"),
url = URL.createObjectURL(file);
a.href = url;
a.download = filename;
document.body.appendChild(a);
a.click();
setTimeout(function() {
document.body.removeChild(a);
window.URL.revokeObjectURL(url);
}, 0);
}
}
Tested to be working properly in Chrome, FireFox and IE10.
In Safari, the data gets opened in a new tab and one would have to manually save this file.
function download(text, name, type) {
var a = document.getElementById("a");
var file = new Blob([text], {type: type});
a.href = URL.createObjectURL(file);
a.download = name;
}
click here to download your file
<button onclick="download('file text', 'myfilename.txt', 'text/plain')">Create file</button>
And you would then download the file by putting the download attribute on the anchor tag.
The reason I like this better than creating a data url is that you don't have to make a big long url, you can just generate a temporary url.
This project on github looks promising:
https://github.com/eligrey/FileSaver.js
FileSaver.js implements the W3C saveAs() FileSaver interface in
browsers that do not natively support it.
Also have a look at the demo here:
http://eligrey.com/demos/FileSaver.js/
Choosing the location to save the file before creating it is not possible. But it is possible, at least in Chrome, to generate files using just JavaScript. Here is an old example of mine of creating a CSV file. The user will be prompted to download it. This, unfortunately, does not work well in other browsers, especially IE.
<!DOCTYPE html>
<html>
<head>
<title>JS CSV</title>
</head>
<body>
<button id="b">export to CSV</button>
<script type="text/javascript">
function exportToCsv() {
var myCsv = "Col1,Col2,Col3\nval1,val2,val3";
window.open('data:text/csv;charset=utf-8,' + escape(myCsv));
}
var button = document.getElementById('b');
button.addEventListener('click', exportToCsv);
</script>
</body>
</html>
For latest browser, like Chrome, you can use the File API as in this tutorial:
window.requestFileSystem = window.requestFileSystem || window.webkitRequestFileSystem;
window.requestFileSystem(window.PERSISTENT, 5*1024*1024 /*5MB*/, saveFile, errorHandler);
function SaveBlobAs(blob, file_name) {
if (typeof navigator.msSaveBlob == "function")
return navigator.msSaveBlob(blob, file_name);
var saver = document.createElementNS("http://www.w3.org/1999/xhtml", "a");
var blobURL = saver.href = URL.createObjectURL(blob),
body = document.body;
saver.download = file_name;
body.appendChild(saver);
saver.dispatchEvent(new MouseEvent("click"));
body.removeChild(saver);
URL.revokeObjectURL(blobURL);
}
Tried this in the console, and it works.
var aFileParts = ['<a id="a"><b id="b">hey!</b></a>'];
var oMyBlob = new Blob(aFileParts, {type : 'text/html'}); // the blob
window.open(URL.createObjectURL(oMyBlob));
You cannot do this purely in Javascript. Javascript running on browsers does not have enough permission yet (there have been proposals) due to security reasons.
Instead, I would recommend using Downloadify:
A tiny javascript + Flash library that enables the creation and download of text files without server interaction.
You can see a simple demo here where you supply the content and can test out saving/cancelling/error handling functionality.
For Chrome and Firefox, I have been using a purely JavaScript method.
(My application cannot make use of a package such as Blob.js because it is served from a special engine: a DSP with a WWWeb server crammed in and little room for anything at all.)
function FileSave(sourceText, fileIdentity) {
var workElement = document.createElement("a");
if ('download' in workElement) {
workElement.href = "data:" + 'text/plain' + "charset=utf-8," + escape(sourceText);
workElement.setAttribute("download", fileIdentity);
document.body.appendChild(workElement);
var eventMouse = document.createEvent("MouseEvents");
eventMouse.initMouseEvent("click", true, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);
workElement.dispatchEvent(eventMouse);
document.body.removeChild(workElement);
} else throw 'File saving not supported for this browser';
}
Notes, caveats, and weasel-words:
I have had success with this code in both Chrome and Firefox clients running in Linux (Maipo) and Windows (7 and 10) environments.
However, if sourceText is larger than a MB, Chrome sometimes (only sometimes) gets stuck in its own download without any failure indication; Firefox, so far, has not exhibited this behavior. The cause might be some blob limitation in Chrome. Frankly, I just don't know; if anybody has any ideas how to correct (or at least detect), please post. If the download anomaly occurs, when the Chrome browser is closed, it generates a diagnostic such as
This code is not compatible with Edge or Internet Explorer; I have not tried Opera or Safari.
StreamSaver is an alternative to save very large files without having to keep all data in the memory.In fact it emulates everything the server dose when saving a file but all client side with service worker.
You can either get the writer and manually write Uint8Array's to it or pipe a binary readableStream to the writable stream
There is a few example showcasing:
How to save multiple files as a zip
piping a readableStream from eg Response or blob.stream() to StreamSaver
manually writing to the writable stream as you type something
or recoding a video/audio
Here is an example in it's simplest form:
const fileStream = streamSaver.createWriteStream('filename.txt')
new Response('StreamSaver is awesome').body
.pipeTo(fileStream)
.then(success, error)
If you want to save a blob you would just convert that to a readableStream
new Response(blob).body.pipeTo(...) // response hack
blob.stream().pipeTo(...) // feature reference
Javascript has a FileSystem API. If you can deal with having the feature only work in Chrome, a good starting point would be: http://www.html5rocks.com/en/tutorials/file/filesystem/.

Firefox - set Blob download source

I am creating a script that lets you download a CSV File of current table on the page like this:
var downloadLink = document.createElement("a");
var blob = new Blob(["", CSVString], {type: 'text/csv;charset=utf-8'});
if (navigator.appVersion.toString().indexOf('.NET') > 0) {
window.navigator.msSaveOrOpenBlob(blob, "Daten.csv");
}
else {
downloadLink.href = window.URL.createObjectURL(blob);
downloadLink.download = "Daten.csv";
downloadLink.style.display = 'none';
document.body.appendChild(downloadLink);
downloadLink.click();
}
Now if I use IE it asks if I want to download a file from localhost, but in Mozilla Firefox the download window says "From: blob:". Can it be changed to show the host name or a name that I specify (e.g. Test)?
Pitifully there's no available solution till the date. The issue was reported a couple of years ago but it seems it has the minor importance level and no one is asigned to this issue.
The From label will always display from: blob::
No matter what you do.

How to show save file dialog in Safari?

I need help. I have an angular app and by using DocRaptor want to generate PDF and save it as file. But I cant trigger the dialog to save file in Safari with any method what I have found on Stack Overflow. Those methods open file in current browser tab and replace site html or open file in new tab. No one cant shows the dialog. Here the examples what I have already tried to use. Environment MacOS - EL Capitan. Safari 9.0.3
Solution #1
var content = 'file content for example';
var blob = new Blob([ content ], { type : 'text/plain' });
$scope.url = (window.URL || window.webkitURL).createObjectURL( blob );
Example jsfiddle. Shows file in current tab. Replaces site. But works in Chrome.
Solution #2
<a target="_self" href="mysite.com/uploads/ahlem.pdf" download="foo.pdf">
Example jsfiddle. Doesnt work at all in Safari. Works in Chrome.
Solution #3
<a class="btn" ng-click="saveJSON()" ng-href="{{ url }}">Export to JSON</a>
and
$scope.saveJSON = function () {
$scope.toJSON = '';
$scope.toJSON = angular.toJson($scope.data);
var blob = new Blob([$scope.toJSON], { type:"application/json;charset=utf-8;" });
var downloadLink = angular.element('<a></a>');
downloadLink.attr('href',window.URL.createObjectURL(blob));
downloadLink.attr('download', 'fileName.json');
downloadLink[0].click();
};
Example Code Snippet. Shows the file content instead of document's html.
Solution #4
function download(text, name, type) {
var a = document.getElementById("a");
var file = new Blob([text], {type: type});
a.href = URL.createObjectURL(file);
a.download = name;
}
Example Code Snippet. Replace document with file content in Safari. Works in Chrome.
And similar Solution #5
function download(text, name, type) {
var a = document.createElement("a");
var file = new Blob([text], {type: type});
a.href = URL.createObjectURL(file);
a.download = name;
a.click();
}
Example jsfiddle. Doesnt work at all in Safari. Works in Chrome.
Also I have tried to use libraries like:
FileSaver - It opens file in Safari instead of document. So you should click Cmd+S. Example.
If we use type 'pplication/octet-stream' the name of file will be unknown or there was be an error 'Failed to load resource: Frame load interrupted'. Issue.
Second library Downloadify - doesnt work in Safari at all. Issue.
Angular library nw-fileDialog - instead of save as it shows choose file. Issue.
DocRaptor has own example with jQuery.
Example with angular in jsfiddle. It works in Chrome but in Safari example doesnt work be cause of error with SAMEORIGIN
Refused to display 'https://docraptor.com/docs' in a frame because it set 'X-Frame-Options' to 'SAMEORIGIN'.
But if we reproduce it on server and change url on 'https://docraptor.com/docs.pdf' it works and open file in new tab and automatically download the file so you cant choose a folder and after download user see white empty screen tab in browser. If we specify form target="_self" it will work perfect, but console will have an error 'Failed to load resource:'.
I will appreciate any help with this problem.
Thanks.
Regards.
Try using Blob file for this:
// Buffer can be response from XMLHttpRequest/Ajax or your custom Int32 data
function download(buffer, filename) {
var file = new Blob([buffer], {
type: 'application/octet-stream' // Replace your mimeType if known
});
var fileReader = new FileReader();
fileReader.onloadend = function(e) {
var converted = e.target.result;
converted.name = filename;
converted.webkitRelativePath = filename;
var iframe = document.createElement('iframe');
iframe.style.display = 'none';
document.body.appendChild(iframe);
iframe.src = converted;
};
fileReader.onerror = function(e) {
throw new Error('Something is wrong with buffer data');
};
fileReader.file = file;
fileReader.readAsDataURL(file);
}
It basically uses filebuffer and download that as an iframe content. Make sure to hook correct mime type so that safari security system will recieved analyse filetype.
Ideally, Solution #2 would be the answer, but the download attribute does not yet have cross-browser support.
So you have to use a <form> to create the download. As you noted, DocRaptor's jQuery example uses this technique.
The SAMEORIGIN error is actually because JSFiddle is running the code in an iFrame with their origin settings. If you run this straight from your Angular application, you shouldn't have any problems.

Replace file blob in browser?

I asked this earlier but someone down voted and accused me of trying to write files to local filesystem without reading.
I have website in an enterprise environment which will only ever be accessed in chrome so keep that in mind.
I am able to select a local folder on my PC and open all sub-folders and files in the browser. I'm using client side javascript to parse these files and look for a particular kind of .xml file that is used internally to render a powerpoint like presentation. I can make changes to this xml file and spit it back out as a blob.
What I would like to do but don't know how is replace the data or blob in the original file with the modified data/blob.
Can the user interact with the data blob? If so, you can use a save file function and overwrite the original.
function saveFile( data )
{
var textFileAsBlob = new Blob([yourData], {type:'text/plain'});
//or replace the code above with your already formed blob
var fileNameToSaveAs = "File_Name_Goes_Here.xml";
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.
try {
downloadLink.href = window.URL.createObjectURL(textFileAsBlob);
downloadLink.onclick = destroyClickedElement;
downloadLink.style.display = "none";
document.body.appendChild(downloadLink);
}
catch( e ){
console.log("error saving firefox file")
}
// IE 10+
try {
window.navigator.msSaveBlob(textFileAsBlob, fileNameToSaveAs);
}
catch(e){
console.log("error saving IE file")
}
}
try {
downloadLink.click();
}
catch(e) {
console.log("Unable to click the download link. Are you using IE?")
}
}
I grabbed this code from somewhere else on stack overflow. I can't remember who it's from though to provide attribution :-(

How to save a png from javascript variable

I have an image encoded in base64 in a javascript variable : data:image/png;base64, base64 data
[EDIT]
I need to save that file to disk without asking to the visitor to do a right click
[/EDIT]
Is it possible ? How ?
Thanks in advance
Best regards
I know this question is 2 years old, but hopefully people will see this update.
You can prompt the user to save an image in a base64 string (and also set the filename), without asking the user to do a right click
var download = document.createElement('a');
download.href = dataURI;
download.download = filename;
download.click();
Example:
var download = document.createElement('a');
download.href = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==';
download.download = 'reddot.png';
download.click();
In order to trigger a click event using Firefox, you need to do what it is explained in this SO answer. Basically:
function fireEvent(obj,evt){
var fireOnThis = obj;
if(document.createEvent ) {
var evObj = document.createEvent('MouseEvents');
evObj.initEvent( evt, true, false );
fireOnThis.dispatchEvent( evObj );
} else if( document.createEventObject ) {
var evObj = document.createEventObject();
fireOnThis.fireEvent( 'on' + evt, evObj );
}
}
fireEvent(download, 'click')
As of 20/03/2013, the only browser that fully supports the download attribute is Chrome. Check the compatibility table here
... without asking to the visitor anyhing ... Is it possible?
No, that would have been a security hole. If it was possible, one would be able to write malware to the enduser's disk unaskingly. Your best bet may be a (signed) Java Applet. True, it costs a bit of $$$ to get it signed (so that it doesn't pop security warnings), but it is able to write data to enduser's disk without its permission.
I am surprised nobody here mentioned using HTML5 blobs together with a couple of nice libraries.
You first need https://github.com/eligrey/FileSaver.js/ and https://github.com/blueimp/JavaScript-Canvas-to-Blob.
Then you can load the image into a canvas
base_image = new Image();
base_image.src ='data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAUAAAAFCAYAAACNbyblAAAAHElEQVQI12P4//8/w38GIAXDIBKE0DHxgljNBAAO9TXL0Y4OHwAAAABJRU5ErkJggg==';
the canvas into a blob
var canvas = document.getElementById('YourCanvas');
context = canvas.getContext('2d');
// Draw image within
context.drawImage(base_image, 0,0);
and finally save it
x_canvas.toBlob(function(blob) {
saveAs(blob, "screenshot.png");
}, "image/png");
FF is not fully supported but at least you get a separate page with the image.
Check this out: http://jsfiddle.net/khhmm/9/
EDIT: this is not compatible with Safari / Mac.
As other answers already stated, you cannot do it only with javascript. If you want, you can send the data (using normal HTTP POST) to a PHP script, call header('Content-type: image/png') and output the decoded image data to the page using echo base64_decode($base64data).
This will work just as if user clicked on an image and open it or prompt him to save the file to disk (the normal browser's save file dialog).
It's not possible.
If it was, browsers would be massively insecure, being able to write random data to your hard disk without user interaction.
with javascript, you can't. the only real possibility i can think of will be a java-applet, but maybe (i don't know how long that image should be saved) you could simply add an img-tag with you png and force caching (but if the user deletes his cache, the image will be gone).
I think it's possible with JavaScript if you use ActiveX.
Another possibility is to make the server spit out that file with a different mime type so the browser asks the user to save it.
I think you can do it something(maybe not only with javascript...xul programming needed). There are Firefox addons that save images to a folder(check Firefox addons site)
You can make this file as blob on the server and use setTimeout function in order to fire the download.
The accepted solution seems to have a limitation for large data. If you're running into this (instead of the downloaded file's name, I see "download" and "Failed - Network error" in Chrome), here's what I did in order to download a 2mb file:
const blob = await (await fetch(document.getElementById('canvasID').toDataURL())).blob();
const file = new File([blob], {type:"image/png", lastModified: new Date()});
var a = document.createElement('a');
a.href = window.URL.createObjectURL(file);
a.download = 'image.png';
a.click();

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