I have a large data in form of JSON object in the javascript. I have converted it into the string using JSON.stringify(). Now my use case is to provide this large string in a text file to the user. So for this i have written below code.
HTML code
<button id='text_feed' type="submit">Generate ION Feed</button>
Javascript code
var text = //huge string
$("#text_feed").click(function() {
_generateFeed(text);
});
var _generateFeed = function(text) {
//some code here
$("#textLink").attr("href",
"data:attachment/txt," + encodeURIComponent(text)) [0].click();
});
};
Problem: When the string length is small , i am able to download the data .
But when the string length goes higher (> 10^5) , my page crashes.
This occurred because "encodeUriComponet(text)" is not able to encode large
data.
I also tried window.open("data:attachment/txt," + encodeURIComponent(text));
But again my page got crashed because of the same reason that encodeURIComponet was unable to encode such a large string.
Another approach: I was also thinking of writing the data into a file using HTML5 File write API , but it has support only in Chrome web browser , but i need to make this work for atleast firefox and chrome both.
Use Case
I don't want to do multiple downloads by breaking the data, as i need to have data in a single file in the end.
And my target is to support string of aprroximately 10^6 length. Can anyone help me how to download/write this amount of data into a single file.
From the OP:
I solved it as below.
var _generateFeed = function(text) {
/*some code here*/
var url = URL.createObjectURL( new Blob( [text], {type:'text/plain'} ) );
$("#textLink").attr("href",url)[0].click();
};
Notes:
URL.createObjectURL() is compatible with modern browsers and IE10+, but it is an unstable, experimental technology.
Objects created using URL.createObjectURL() "must be released by calling URL.revokeObjectURL() when you no longer need them." - MDN
Related
I want to display OpenOffice files, .odt and .odp at client side using a web browser.
These files are zipped files. Using Ajax, I can get these files from server but these are zipped files. I have to unzip them using JavaScript, I have tried using inflate.js, http://www.onicos.com/staff/iz/amuse/javascript/expert/inflate.txt, but without success.
How can I do this?
I wrote an unzipper in Javascript. It works.
It relies on Andy G.P. Na's binary file reader and some RFC1951 inflate logic from notmasteryet. I added the ZipFile class.
working example:
http://cheeso.members.winisp.net/Unzip-Example.htm (dead link)
The source:
http://cheeso.members.winisp.net/srcview.aspx?dir=js-unzip (dead link)
NB: the links are dead; I'll find a new host soon.
Included in the source is a ZipFile.htm demonstration page, and 3 distinct scripts, one for the zipfile class, one for the inflate class, and one for a binary file reader class. The demo also depends on jQuery and jQuery UI. If you just download the js-zip.zip file, all of the necessary source is there.
Here's what the application code looks like in Javascript:
// In my demo, this gets attached to a click event.
// it instantiates a ZipFile, and provides a callback that is
// invoked when the zip is read. This can take a few seconds on a
// large zip file, so it's asynchronous.
var readFile = function(){
$("#status").html("<br/>");
var url= $("#urlToLoad").val();
var doneReading = function(zip){
extractEntries(zip);
};
var zipFile = new ZipFile(url, doneReading);
};
// this function extracts the entries from an instantiated zip
function extractEntries(zip){
$('#report').accordion('destroy');
// clear
$("#report").html('');
var extractCb = function(id) {
// this callback is invoked with the entry name, and entry text
// in my demo, the text is just injected into an accordion panel.
return (function(entryName, entryText){
var content = entryText.replace(new RegExp( "\\n", "g" ), "<br/>");
$("#"+id).html(content);
$("#status").append("extract cb, entry(" + entryName + ") id(" + id + ")<br/>");
$('#report').accordion('destroy');
$('#report').accordion({collapsible:true, active:false});
});
}
// for each entry in the zip, extract it.
for (var i=0; i<zip.entries.length; i++) {
var entry = zip.entries[i];
var entryInfo = "<h4><a>" + entry.name + "</a></h4>\n<div>";
// contrive an id for the entry, make it unique
var randomId = "id-"+ Math.floor((Math.random() * 1000000000));
entryInfo += "<span class='inputDiv'><h4>Content:</h4><span id='" + randomId +
"'></span></span></div>\n";
// insert the info for one entry as the last child within the report div
$("#report").append(entryInfo);
// extract asynchronously
entry.extract(extractCb(randomId));
}
}
The demo works in a couple of steps: The readFile fn is triggered by a click, and instantiates a ZipFile object, which reads the zip file. There's an asynchronous callback for when the read completes (usually happens in less than a second for reasonably sized zips) - in this demo the callback is held in the doneReading local variable, which simply calls extractEntries, which
just blindly unzips all the content of the provided zip file. In a real app you would probably choose some of the entries to extract (allow the user to select, or choose one or more entries programmatically, etc).
The extractEntries fn iterates over all entries, and calls extract() on each one, passing a callback. Decompression of an entry takes time, maybe 1s or more for each entry in the zipfile, which means asynchrony is appropriate. The extract callback simply adds the extracted content to an jQuery accordion on the page. If the content is binary, then it gets formatted as such (not shown).
It works, but I think that the utility is somewhat limited.
For one thing: It's very slow. Takes ~4 seconds to unzip the 140k AppNote.txt file from PKWare. The same uncompress can be done in less than .5s in a .NET program. EDIT: The Javascript ZipFile unpacks considerably faster than this now, in IE9 and in Chrome. It is still slower than a compiled program, but it is plenty fast for normal browser usage.
For another: it does not do streaming. It basically slurps in the entire contents of the zipfile into memory. In a "real" programming environment you could read in only the metadata of a zip file (say, 64 bytes per entry) and then read and decompress the other data as desired. There's no way to do IO like that in javascript, as far as I know, therefore the only option is to read the entire zip into memory and do random access in it. This means it will place unreasonable demands on system memory for large zip files. Not so much a problem for a smaller zip file.
Also: It doesn't handle the "general case" zip file - there are lots of zip options that I didn't bother to implement in the unzipper - like ZIP encryption, WinZip encryption, zip64, UTF-8 encoded filenames, and so on. (EDIT - it handles UTF-8 encoded filenames now). The ZipFile class handles the basics, though. Some of these things would not be hard to implement. I have an AES encryption class in Javascript; that could be integrated to support encryption. Supporting Zip64 would probably useless for most users of Javascript, as it is intended to support >4gb zipfiles - don't need to extract those in a browser.
I also did not test the case for unzipping binary content. Right now it unzips text. If you have a zipped binary file, you'd need to edit the ZipFile class to handle it properly. I didn't figure out how to do that cleanly. It does binary files now, too.
EDIT - I updated the JS unzip library and demo. It now does binary files, in addition to text. I've made it more resilient and more general - you can now specify the encoding to use when reading text files. Also the demo is expanded - it shows unzipping an XLSX file in the browser, among other things.
So, while I think it is of limited utility and interest, it works. I guess it would work in Node.js.
I'm using zip.js and it seems to be quite useful. It's worth a look!
Check the Unzip demo, for example.
I found jszip quite useful. I've used so far only for reading, but they have create/edit capabilities as well.
Code wise it looks something like this
var new_zip = new JSZip();
new_zip.load(file);
new_zip.files["doc.xml"].asText() // this give you the text in the file
One thing I noticed is that it seems the file has to be in binary stream format (read using the .readAsArrayBuffer of FileReader(), otherwise I was getting errors saying I might have a corrupt zip file
Edit: Note from the 2.x to 3.0.0 upgrade guide:
The load() method and the constructor with data (new JSZip(data)) have
been replaced by loadAsync().
Thanks user2677034
If you need to support other formats as well or just need good performance, you can use this WebAssembly library
it's promised based, it uses WebWorkers for threading and API is actually simple ES module
How to use
Install with npm i libarchive.js and use it as a ES module.
The library consists of two parts: ES module and webworker bundle, ES module part is your interface to talk to library, use it like any other module. The webworker bundle lives in the libarchive.js/dist folder so you need to make sure that it is available in your public folder since it will not get bundled if you're using bundler (it's all bundled up already) and specify correct path to Archive.init() method.
import {Archive} from 'libarchive.js/main.js';
Archive.init({
workerUrl: 'libarchive.js/dist/worker-bundle.js'
});
document.getElementById('file').addEventListener('change', async (e) => {
const file = e.currentTarget.files[0];
const archive = await Archive.open(file);
let obj = await archive.extractFiles();
console.log(obj);
});
// outputs
{
".gitignore": {File},
"addon": {
"addon.py": {File},
"addon.xml": {File}
},
"README.md": {File}
}
I wrote "Binary Tools for JavaScript", an open source project that includes the ability to unzip, unrar and untar: https://github.com/codedread/bitjs
Used in my comic book reader: https://github.com/codedread/kthoom (also open source).
HTH!
If anyone's reading images or other binary files from a zip file hosted at a remote server, you can use following snippet to download and create zip object using the jszip library.
// this function just get the public url of zip file.
let url = await getStorageUrl(path)
console.log('public url is', url)
//get the zip file to client
axios.get(url, { responseType: 'arraybuffer' }).then((res) => {
console.log('zip download status ', res.status)
//load contents into jszip and create an object
jszip.loadAsync(new Blob([res.data], { type: 'application/zip' })).then((zip) => {
const zipObj = zip
$.each(zip.files, function (index, zipEntry) {
console.log('filename', zipEntry.name)
})
})
Now using the zipObj you can access the files and create a src url for it.
var fname = 'myImage.jpg'
zipObj.file(fname).async('blob').then((blob) => {
var blobUrl = URL.createObjectURL(blob)
I have copied an Excel table which is about a million rows. When I look at the clipboard on my system, it seems to contain about 250MB of data. However, I only need to grab the styling information from it, for example:
This entire data comes out to (far) less than 1MB of data. Is there a way to read the clipboard as if it were a file or stream, so that I can just do, for example:
clipboard.read(1024)
Otherwise, if I do the straight:
evt.clipboardData.getData('text/html')
And grab the section of data I want after getting the data, it takes me over 10 seconds to do! Whereas I believe the event should only take 0.1s or so, if I'm able to read the clipboard data in a partial manner, as if it were a file.
What can I do here? Is it possible to use FileReader on the clipboard? If so, how could that be done?
The Clipboard.read API cited in the comments can return clipboard contents as a list of ClipboardItem objects, from which you can then obtain a Blob object, which you can then .slice to perform partial reads. (The MDN claims that Clipboard.read returns a DataTransfer object, but this disagrees with the specification, so I assume this is stale information, or simply in error.)
const perm = await navigator.permissions.query({ name: 'clipboard-read' });
switch (perm.state) {
case 'granted':
case 'prompt':
break;
default:
throw new Error("clipboard-read permission not granted");
}
const items = await navigator.clipboard.read();
for (const item of items) {
const blob = await item.getType('text/html');
const first1M = await blob.slice(0, 1048576).arrayBuffer();
/* process first1M */
}
However, the Clipboard API is nowhere near universally available as of yet. Firefox ESR 78.9 doesn’t implement it, and by the state of MDN it hardly seems to be on Mozilla’s radar at all. (I haven’t tried other browsers yet; perhaps in Chrome it’s already usable.)
After a lot a research, this is not possible in Javascript, there is no support for stream manipulation using the clipboard object so u have to read the entire content at once.
However, u can use MacOS (inferred from your picture) native tools for processing the clipboard data: pbcopy and pbpaste, and they are extremely fast, orders of magnitude faster than Javascript, so u can delegate the heavy processing of the text to them.
So, after u copy the 250MB of text, you can slice it and read only the first n bytes (in this case 1024) and substitute the content of the clipboard with that, so now u it will be available for u to use it in Javascript:
pbpaste | cut -b 1-1024 | pbcopy
If u need any documentation about each terminal command, u can run man command_name. Extracting the first 1024 bytes of the clipboard took less than a second with this approach.
I tested it with a sample text file of 390MB created with python with this script:
c = 30000000
with open('sample.txt', 'w') as file:
file.writelines('a sample code' for i in range(c))
I have a Javascript program that extracts data from a text file (just a plain *.txt file) and then displays it in a table. It works as intended except for one issue: If I update the text file where the data lives in the update does not shows up on the table. The reason is that the file is being cached by the browser.
Is there a way to force Javascript to read from the latest version of the file and not from the cached version? Again, this is not a problem with the javascript file as doing Ctrl-5 and or Shift+Ctrl+R does not works and also updating the javascript file itself behaves as expected. it is only the file where the data is in that is the problem.
To read the text file I use the Webix toolkit which uses AJAX to read the file. The reading and parsing of the text file is done via Javascript and the Webix toolkit. There is very little html in my program.
//the name of the file is dependant of an user specified input
var theURL = rossObj.store_number.store_number + "macaddress.txt ";
webix.ajax(theURL,{
//response
error:function(text, xml, XmlHttpRequest){
webix.alert({ ok:"OK", type:"alert-warning", text:"could not open the following URL --> "+theURL, width:"400px"});
return "mac_address_error";
},
success:function(text, xml, XmlHttpRequest){
//parse the file;
}
});
Try adding a random number to the end of the url as a query string, the server will ignore but the browser will treat it as a new file
var theURL = rossObj.store_number.store_number +
"macaddress.txt?" +
Math.floor((Math.random() * 10000) + 1);
I'm receiving a JSON output from an API, and i want to use it with JS and also save that output to file. Is there any way to trigger the browser download machanism using JS with thet output?
Maybe now some browsers support the attribute download but you don't trigger the browser to automatically download the file.
the only way i know is #BAS's solution but without a filename.
tested in chrome ..
array=[{a:'1',b:'2'},{x:'3',y:'4'}];
function dl(array,filename){
var b=document.createElement('a');
b.download=filename;
b.textContent=filename;
b.href='data:application/json;base64,'+
window.btoa(unescape(encodeURIComponent(JSON.stringify(array))))
// or
// b.href='data:application/javascript;charset=utf-8,'+JSON.stringify(json);
return b
}
document.body.appendChild(dl(array,'my.json'));
example
http://jsfiddle.net/8yQcW/
UPDATE direct download works ... on chrome i tested.
on append simulate click
var e=document.createEvent('Events');
e.initEvent('click',true,false);
document.getElementById('dl').dispatchEvent(e);
http://jsfiddle.net/8yQcW/1/
You could try it with a data URI:
function triggerDownload(json) {
var dataUri = 'data:text;charset=utf-8,' + json;
window.open(dataUri);
}
Try entering data:text;charset=utf-8,{"Key":"Value"} into your browsers address bar. It should show you the save dialog.
See here for more information and browser support.
I want to display OpenOffice files, .odt and .odp at client side using a web browser.
These files are zipped files. Using Ajax, I can get these files from server but these are zipped files. I have to unzip them using JavaScript, I have tried using inflate.js, http://www.onicos.com/staff/iz/amuse/javascript/expert/inflate.txt, but without success.
How can I do this?
I wrote an unzipper in Javascript. It works.
It relies on Andy G.P. Na's binary file reader and some RFC1951 inflate logic from notmasteryet. I added the ZipFile class.
working example:
http://cheeso.members.winisp.net/Unzip-Example.htm (dead link)
The source:
http://cheeso.members.winisp.net/srcview.aspx?dir=js-unzip (dead link)
NB: the links are dead; I'll find a new host soon.
Included in the source is a ZipFile.htm demonstration page, and 3 distinct scripts, one for the zipfile class, one for the inflate class, and one for a binary file reader class. The demo also depends on jQuery and jQuery UI. If you just download the js-zip.zip file, all of the necessary source is there.
Here's what the application code looks like in Javascript:
// In my demo, this gets attached to a click event.
// it instantiates a ZipFile, and provides a callback that is
// invoked when the zip is read. This can take a few seconds on a
// large zip file, so it's asynchronous.
var readFile = function(){
$("#status").html("<br/>");
var url= $("#urlToLoad").val();
var doneReading = function(zip){
extractEntries(zip);
};
var zipFile = new ZipFile(url, doneReading);
};
// this function extracts the entries from an instantiated zip
function extractEntries(zip){
$('#report').accordion('destroy');
// clear
$("#report").html('');
var extractCb = function(id) {
// this callback is invoked with the entry name, and entry text
// in my demo, the text is just injected into an accordion panel.
return (function(entryName, entryText){
var content = entryText.replace(new RegExp( "\\n", "g" ), "<br/>");
$("#"+id).html(content);
$("#status").append("extract cb, entry(" + entryName + ") id(" + id + ")<br/>");
$('#report').accordion('destroy');
$('#report').accordion({collapsible:true, active:false});
});
}
// for each entry in the zip, extract it.
for (var i=0; i<zip.entries.length; i++) {
var entry = zip.entries[i];
var entryInfo = "<h4><a>" + entry.name + "</a></h4>\n<div>";
// contrive an id for the entry, make it unique
var randomId = "id-"+ Math.floor((Math.random() * 1000000000));
entryInfo += "<span class='inputDiv'><h4>Content:</h4><span id='" + randomId +
"'></span></span></div>\n";
// insert the info for one entry as the last child within the report div
$("#report").append(entryInfo);
// extract asynchronously
entry.extract(extractCb(randomId));
}
}
The demo works in a couple of steps: The readFile fn is triggered by a click, and instantiates a ZipFile object, which reads the zip file. There's an asynchronous callback for when the read completes (usually happens in less than a second for reasonably sized zips) - in this demo the callback is held in the doneReading local variable, which simply calls extractEntries, which
just blindly unzips all the content of the provided zip file. In a real app you would probably choose some of the entries to extract (allow the user to select, or choose one or more entries programmatically, etc).
The extractEntries fn iterates over all entries, and calls extract() on each one, passing a callback. Decompression of an entry takes time, maybe 1s or more for each entry in the zipfile, which means asynchrony is appropriate. The extract callback simply adds the extracted content to an jQuery accordion on the page. If the content is binary, then it gets formatted as such (not shown).
It works, but I think that the utility is somewhat limited.
For one thing: It's very slow. Takes ~4 seconds to unzip the 140k AppNote.txt file from PKWare. The same uncompress can be done in less than .5s in a .NET program. EDIT: The Javascript ZipFile unpacks considerably faster than this now, in IE9 and in Chrome. It is still slower than a compiled program, but it is plenty fast for normal browser usage.
For another: it does not do streaming. It basically slurps in the entire contents of the zipfile into memory. In a "real" programming environment you could read in only the metadata of a zip file (say, 64 bytes per entry) and then read and decompress the other data as desired. There's no way to do IO like that in javascript, as far as I know, therefore the only option is to read the entire zip into memory and do random access in it. This means it will place unreasonable demands on system memory for large zip files. Not so much a problem for a smaller zip file.
Also: It doesn't handle the "general case" zip file - there are lots of zip options that I didn't bother to implement in the unzipper - like ZIP encryption, WinZip encryption, zip64, UTF-8 encoded filenames, and so on. (EDIT - it handles UTF-8 encoded filenames now). The ZipFile class handles the basics, though. Some of these things would not be hard to implement. I have an AES encryption class in Javascript; that could be integrated to support encryption. Supporting Zip64 would probably useless for most users of Javascript, as it is intended to support >4gb zipfiles - don't need to extract those in a browser.
I also did not test the case for unzipping binary content. Right now it unzips text. If you have a zipped binary file, you'd need to edit the ZipFile class to handle it properly. I didn't figure out how to do that cleanly. It does binary files now, too.
EDIT - I updated the JS unzip library and demo. It now does binary files, in addition to text. I've made it more resilient and more general - you can now specify the encoding to use when reading text files. Also the demo is expanded - it shows unzipping an XLSX file in the browser, among other things.
So, while I think it is of limited utility and interest, it works. I guess it would work in Node.js.
I'm using zip.js and it seems to be quite useful. It's worth a look!
Check the Unzip demo, for example.
I found jszip quite useful. I've used so far only for reading, but they have create/edit capabilities as well.
Code wise it looks something like this
var new_zip = new JSZip();
new_zip.load(file);
new_zip.files["doc.xml"].asText() // this give you the text in the file
One thing I noticed is that it seems the file has to be in binary stream format (read using the .readAsArrayBuffer of FileReader(), otherwise I was getting errors saying I might have a corrupt zip file
Edit: Note from the 2.x to 3.0.0 upgrade guide:
The load() method and the constructor with data (new JSZip(data)) have
been replaced by loadAsync().
Thanks user2677034
If you need to support other formats as well or just need good performance, you can use this WebAssembly library
it's promised based, it uses WebWorkers for threading and API is actually simple ES module
How to use
Install with npm i libarchive.js and use it as a ES module.
The library consists of two parts: ES module and webworker bundle, ES module part is your interface to talk to library, use it like any other module. The webworker bundle lives in the libarchive.js/dist folder so you need to make sure that it is available in your public folder since it will not get bundled if you're using bundler (it's all bundled up already) and specify correct path to Archive.init() method.
import {Archive} from 'libarchive.js/main.js';
Archive.init({
workerUrl: 'libarchive.js/dist/worker-bundle.js'
});
document.getElementById('file').addEventListener('change', async (e) => {
const file = e.currentTarget.files[0];
const archive = await Archive.open(file);
let obj = await archive.extractFiles();
console.log(obj);
});
// outputs
{
".gitignore": {File},
"addon": {
"addon.py": {File},
"addon.xml": {File}
},
"README.md": {File}
}
I wrote "Binary Tools for JavaScript", an open source project that includes the ability to unzip, unrar and untar: https://github.com/codedread/bitjs
Used in my comic book reader: https://github.com/codedread/kthoom (also open source).
HTH!
If anyone's reading images or other binary files from a zip file hosted at a remote server, you can use following snippet to download and create zip object using the jszip library.
// this function just get the public url of zip file.
let url = await getStorageUrl(path)
console.log('public url is', url)
//get the zip file to client
axios.get(url, { responseType: 'arraybuffer' }).then((res) => {
console.log('zip download status ', res.status)
//load contents into jszip and create an object
jszip.loadAsync(new Blob([res.data], { type: 'application/zip' })).then((zip) => {
const zipObj = zip
$.each(zip.files, function (index, zipEntry) {
console.log('filename', zipEntry.name)
})
})
Now using the zipObj you can access the files and create a src url for it.
var fname = 'myImage.jpg'
zipObj.file(fname).async('blob').then((blob) => {
var blobUrl = URL.createObjectURL(blob)