I've been fiddling with WebGL lately, and have gotten a Collada reader working. Problem is it's pretty slow (Collada is a very verbose format), so I'm going to start converting files to a easier to use format (probably JSON). I already have the code to parse the file in JavaScript, so I may as well use it as my exporter too! The problem is saving.
Now, I know that I can parse the file, send the result to the server, and have the browser request the file back from the server as a download. But in reality the server has nothing to do with this particular process, so why get it involved? I already have the contents of the desired file in memory. Is there any way that I could present the user with a download using pure JavaScript? (I doubt it, but might as well ask...)
And to be clear: I am not trying to access the filesystem without the users knowledge! The user will provide a file (probably via drag and drop), the script will transform the file in memory, and the user will be prompted to download the result. All of which should be "safe" activities as far as the browser is concerned.
[EDIT]: I didn't mention it upfront, so the posters who answered "Flash" are valid enough, but part of what I'm doing is an attempt to highlight what can be done with pure HTML5... so Flash is right out in my case. (Though it's a perfectly valid answer for anyone doing a "real" web app.) That being the case it looks like I'm out of luck unless I want to involve the server. Thanks anyway!
This question is related to
javascript
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download
HTML5 defined a window.saveAs(blob, filename) method. It isn't supported by any browser right now. But there is a compatibility library called FileSaver.js that adds this function to most modern browsers (including Internet Explorer 10+). Internet Explorer 10 supports a navigator.msSaveBlob(blob, filename) method (MSDN), which is used in FileSaver.js for Internet Explorer support.
I wrote a blog posting with more details about this problem.
I found two simple approaches that work for me. First, using an already clicked a element and injecting the download data. And second, generating an a element with the download data, executing a.click() and removing it again. But the second approach works only if invoked by a user click action as well. (Some) Browser block click() from other contexts like on loading or triggered after a timeout (setTimeout).
<!DOCTYPE HTML>
<html>
<head>
<meta charset="UTF-8">
<script type="text/javascript">
function linkDownload(a, filename, content) {
contentType = 'data:application/octet-stream,';
uriContent = contentType + encodeURIComponent(content);
a.setAttribute('href', uriContent);
a.setAttribute('download', filename);
}
function download(filename, content) {
var a = document.createElement('a');
linkDownload(a, filename, content);
document.body.appendChild(a);
a.click();
document.body.removeChild(a);
}
</script>
</head>
<body>
<a href="#" onclick="linkDownload(this, 'test.txt', 'Hello World!');">download</a>
<button onclick="download('test.txt', 'Hello World!');">download</button>
</body>
</html>
Here is a link to the data URI method Mathew suggested, it worked on safari, but not well because I couldn't set the filetype, it gets saved as "unknown" and then i have to go there again later and change it in order to view the file...
Long data URIs can give performance problems in browsers. Another option to save client-side generated files, is to put their contents in a Blob (or File) object and create a download link using URL.createObjectURL(blob). This returns an URL that can be used to retrieve the contents of the blob. The blob is stored inside the browser until either URL.revokeObjectURL() is called on the URL or the document that created it is closed. Most web browsers have support for object URLs, Opera Mini is the only one that does not support them.
If the data is text or an image, the browser can open the file, instead of saving it to disk. To cause the file to be downloaded upon clicking the link, you can use the the download attribute. However, not all web browsers have support for the download attribute. Another option is to use application/octet-stream as the file's mime-type, but this causes the file to be presented as a binary blob which is especially user-unfriendly if you don't or can't specify a filename. See also 'Force to open "Save As..." popup open at text link click for pdf in HTML'.
If the blob is created with the File constructor, you can also set a filename, but only a few web browsers (including Chrome & Firefox) have support for the File constructor. The filename can also be specified as the argument to the download attribute, but this is subject to a ton of security considerations. Internet Explorer 10 and 11 provides its own method, msSaveBlob, to specify a filename.
var file;_x000D_
var data = [];_x000D_
data.push("This is a test\n");_x000D_
data.push("Of creating a file\n");_x000D_
data.push("In a browser\n");_x000D_
var properties = {type: 'text/plain'}; // Specify the file's mime-type._x000D_
try {_x000D_
// Specify the filename using the File constructor, but ..._x000D_
file = new File(data, "file.txt", properties);_x000D_
} catch (e) {_x000D_
// ... fall back to the Blob constructor if that isn't supported._x000D_
file = new Blob(data, properties);_x000D_
}_x000D_
var url = URL.createObjectURL(file);_x000D_
document.getElementById('link').href = url;<a id="link" target="_blank" download="file.txt">Download</a>I've used FileSaver (https://github.com/eligrey/FileSaver.js) and it works just fine.
For example, I did this function to export logs displayed on a page.
You have to pass an array for the instanciation of the Blob, so I just maybe didn't write this the right way, but it works for me.
Just in case, be careful with the replace: this is the syntax to make this global, otherwise it will only replace the first one he meets.
exportLogs : function(){
var array = new Array();
var str = $('#logs').html();
array[0] = str.replace(/<br>/g, '\n\t');
var blob = new Blob(array, {type: "text/plain;charset=utf-8"});
saveAs(blob, "example.log");
}
You can generate a data URI. However, there are browser-specific limitations.
function download(content, filename, contentType)
{
if(!contentType) contentType = 'application/octet-stream';
var a = document.createElement('a');
var blob = new Blob([content], {'type':contentType});
a.href = window.URL.createObjectURL(blob);
a.download = filename;
a.click();
}
As previously mentioned the File API, along with the FileWriter and FileSystem APIs can be used to store files on a client's machine from the context of a browser tab/window.
However, there are several things pertaining to latter two APIs which you should be aware of:
Here are simple examples of how the APIs are used, directly and indirectly, in tandem to do this:
bakedGoods.get({
data: ["testFile"],
storageTypes: ["fileSystem"],
options: {fileSystem:{storageType: Window.PERSISTENT}},
complete: function(resultDataObj, byStorageTypeErrorObj){}
});
Using the raw File, FileWriter, and FileSystem APIs
function onQuotaRequestSuccess(grantedQuota)
{
function saveFile(directoryEntry)
{
function createFileWriter(fileEntry)
{
function write(fileWriter)
{
var dataBlob = new Blob(["Hello world!"], {type: "text/plain"});
fileWriter.write(dataBlob);
}
fileEntry.createWriter(write);
}
directoryEntry.getFile(
"testFile",
{create: true, exclusive: true},
createFileWriter
);
}
requestFileSystem(Window.PERSISTENT, grantedQuota, saveFile);
}
var desiredQuota = 1024 * 1024 * 1024;
var quotaManagementObj = navigator.webkitPersistentStorage;
quotaManagementObj.requestQuota(desiredQuota, onQuotaRequestSuccess);
Though the FileSystem and FileWriter APIs are no longer on the standards track, their use can be justified in some cases, in my opinion, because:
Whether "some cases" encompasses your own, however, is for you to decide.
*BakedGoods is maintained by none other than this guy right here :)
You can use localStorage. This is the Html5 equivalent of cookies. It appears to work on Chrome and Firefox BUT on Firefox, I needed to upload it to a server. That is, testing directly on my home computer didn't work.
I'm working up HTML5 examples. Go to http://faculty.purchase.edu/jeanine.meyer/html5/html5explain.html and scroll to the maze one. The information to re-build the maze is stored using localStorage.
I came to this article looking for HTML5 JavaScript for loading and working with xml files. Is it the same as older html and JavaScript????
Take a look at Doug Neiner's Downloadify which is a Flash based JavaScript interface to do this.
Downloadify is a tiny JavaScript + Flash library that enables the generation and saving of files on the fly, in the browser, without server interaction.
This thread was invaluable to figure out how to generate a binary file and prompt to download the named file, all in client code without a server.
First step for me was generating the binary blob from data that I was saving. There's plenty of samples for doing this for a single binary type, in my case I have a binary format with multiple types which you can pass as an array to create the blob.
saveAnimation: function() {
var device = this.Device;
var maxRow = ChromaAnimation.getMaxRow(device);
var maxColumn = ChromaAnimation.getMaxColumn(device);
var frames = this.Frames;
var frameCount = frames.length;
var writeArrays = [];
var writeArray = new Uint32Array(1);
var version = 1;
writeArray[0] = version;
writeArrays.push(writeArray.buffer);
//console.log('version:', version);
var writeArray = new Uint8Array(1);
var deviceType = this.DeviceType;
writeArray[0] = deviceType;
writeArrays.push(writeArray.buffer);
//console.log('deviceType:', deviceType);
var writeArray = new Uint8Array(1);
writeArray[0] = device;
writeArrays.push(writeArray.buffer);
//console.log('device:', device);
var writeArray = new Uint32Array(1);
writeArray[0] = frameCount;
writeArrays.push(writeArray.buffer);
//console.log('frameCount:', frameCount);
for (var index = 0; index < frameCount; ++index) {
var frame = frames[index];
var writeArray = new Float32Array(1);
var duration = frame.Duration;
if (duration < 0.033) {
duration = 0.033;
}
writeArray[0] = duration;
writeArrays.push(writeArray.buffer);
//console.log('Frame', index, 'duration', duration);
var writeArray = new Uint32Array(maxRow * maxColumn);
for (var i = 0; i < maxRow; ++i) {
for (var j = 0; j < maxColumn; ++j) {
var color = frame.Colors[i][j];
writeArray[i * maxColumn + j] = color;
}
}
writeArrays.push(writeArray.buffer);
}
var blob = new Blob(writeArrays, {type: 'application/octet-stream'});
return blob;
}
The next step is to get the browser to prompt the user to download this blob with a predefined name.
All I needed was a named link I added in the HTML5 that I could reuse to rename the initial filename. I kept it hidden since the link doesn't need display.
<a id="lnkDownload" style="display: none" download="client.chroma" href="" target="_blank"></a>
The last step is to prompt the user to download the file.
var data = animation.saveAnimation();
var uriContent = URL.createObjectURL(data);
var lnkDownload = document.getElementById('lnkDownload');
lnkDownload.download = 'theDefaultFileName.extension';
lnkDownload.href = uriContent;
lnkDownload.click();
try
let a = document.createElement('a');
a.href = "data:application/octet-stream,"+encodeURIComponent('"My DATA"');
a.download = 'myFile.json';
a.click(); // we not add 'a' to DOM so no need to removeIf you want to download binary data look here
2020.06.14 I upgrade Chrome to 83.0 and above SO snippet stop works (due to sandbox security restrictions) - but JSFiddle version works - here
Simple solution for HTML5 ready browsers...
function download(filename, text) {
var pom = document.createElement('a');
pom.setAttribute('href', 'data:text/plain;charset=utf-8,' + encodeURIComponent(text));
pom.setAttribute('download', filename);
if (document.createEvent) {
var event = document.createEvent('MouseEvents');
event.initEvent('click', true, true);
pom.dispatchEvent(event);
}
else {
pom.click();
}
}
Usage
download('test.txt', 'Hello world!');
<a download="My-FileName.txt" href="data:application/octet-stream,HELLO-WORLDDDDDDDD">Click here</a>Works in all Modern browsers.
Here is a tutorial to export files as ZIP:
Before getting started, there is a library to save files, the name of library is fileSaver.js, You can find this library here. Let's get started, Now, include the required libraries:
<script src="https://cdnjs.cloudflare.com/ajax/libs/jszip/3.1.4/jszip.min.js" type="text/javascript"></script>
<script type="text/javascript" src="https://fastcdn.org/FileSaver.js/1.1.20151003/FileSaver.js" ></script>
Now copy this code and this code will download a zip file with a file hello.txt having content Hello World. If everything thing works fine, this will download a file.
<script type="text/javascript">
var zip = new JSZip();
zip.file("Hello.txt", "Hello World\n");
zip.generateAsync({type:"blob"})
.then(function(content) {
// see FileSaver.js
saveAs(content, "file.zip");
});
</script>
This will download a file called file.zip. You can read more here: http://www.wapgee.com/story/248/guide-to-create-zip-files-using-javascript-by-using-jszip-library
When testing the "ahref" method, I found that the web developer tools of Firefox and Chrome gets confused. I needed to restart the debugging after the a.click() was issued. Same happened with the FileSaver (it uses the same ahref method to actually make the saving). To work around it, I created new temporary window, added the element a into that and clicked it there.
function download_json(dt) {
var csv = ' var data = ';
csv += JSON.stringify(dt, null, 3);
var uricontent = 'data:application/octet-stream,' + encodeURI(csv);
var newwin = window.open( "", "_blank" );
var elem = newwin.document.createElement('a');
elem.download = "database.js";
elem.href = uricontent;
elem.click();
setTimeout(function(){ newwin.close(); }, 3000);
}
Source: Stackoverflow.com