Develop Reference

Normalize file path in JavaScript front-end

The short story:
Is there simple way to normalize file path in JavaScript, like in Java we have Paths.get("/a/b/../c").normalize() so /a/../../c would become /c. I seen many same questions here, but they are Node.js solutions, and I need pure JS or JQuery approach so it can be used in browser.
The long story:
I have a file server with web UI, that allows to browse files and download them. UI is written in spring and accessible at mysite.com/ui/
The file storage located at mysite.com/files/ which is plain Apache directory, so its possible to get direct link to file.
The real storage directory on server is /var/www/files
Path passing to back-end as mysite.com/ui/?path=/a/../../c, so back-end will normalize path variable separately to /c and then append it to base dir and so retrieving content of /home/storage/c, so it works perfectly.
The problem comes when user tries to download file like this with direct link. I.e. if user tries to download /a/../../c/d file from file server root, it appending to base storage url, which mysite.com/files/, and it becomes mysite.com/files/a/../../c/d so it will point to /var/www/d instead of /var/www/files/d so file can't be downloaded even if it is visible from web UI.
So I need to normalize relative file path first on front-end like on back-end when retrieving content of directory but I don't know how it can be done in JS. Is there function for it, or I have to write my own one?

So I ended up writing my own function on JS. It might be not what "path normalization" stands for, but anyway its exactly what I need
function normalizePath(path) {
// remove multiple slashes
path = path.replace(/\/+/g, '/');
// remove leading slash, will be added further
if (path.startsWith("/"))
path = path.substring(1)
// remove trailing slash
if (path.endsWith("/"))
path = path.slice(0, -1);
let segments = path.split("/");
let normalizedPath = "/";
for (let segmentIndex = 0; segmentIndex < segments.length; segmentIndex++) {
if (segments[segmentIndex] === "." || segments[segmentIndex] === "") {
// skip single dots and empty segments
continue;
}
if (segments[segmentIndex] === "..") {
// go up one level if possible
normalizedPath = normalizedPath.substring(0, normalizedPath.lastIndexOf("/") + 1);
continue;
}
// append path segment
if (!normalizedPath.endsWith("/"))
normalizedPath = normalizedPath + "/"
normalizedPath = normalizedPath + segments[segmentIndex];
}
return normalizedPath;
}
Still, I won't mark this as accepted answer as it's more of a quick fix, and I'm not JS expert so it definitely must be more elegant solution.

Unzip a zip file with JavaScript [duplicate]

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)

Compressing Base64 string through LZString gives SyntaxErrors

https://pieroxy.net/blog/pages/lz-string/guide.html
I have some Base64 data url strings which need to be compressed into shorter strings. I have downloaded the LZString library and tried to use Base64String.compress(base64) and Base64String.decompress(compressedBase64) as demonstrated in above official guide.
While the data urls are used for displaying images in offline page, the page is expected to be in compressed size, so each string has to be decompressed within the offline page. Here is a simplified code sample:
var compressed = Base64String.compress(dataUrl);
var script = document.createElement("script");
script.innerHTML = "var dataUrl = Base64String.decompress(" + compressed + ");";
offlineHtml.querySelector("body").appendChild(script);
However, when I download the page and open it, it shows various forms of SyntaxErrors occurred, including missing ) after argument list Invalid or unexpected token Unexpected identifiers. It seems that the string is compressed in a way that creates problematic syntax. Is there any solution, or any other suitable library for base64 string compression?

Instead of trying to concatenate to create a string containing valid Javascript syntax, save the compressed string somewhere else from which static Javascript can retrieve and parse it. You could use <script type="application/json">, or an invisible textarea, or a data attribute:
const compressed = Base64String.compress(dataUrl);
const script = document.createElement("script");
script.dataset.compressed = compressed;
script.textContent = `
var dataUrl = Base64String.decompress(document.currentScript.dataset.compressed);
`;
offlineHtml.querySelector("body").appendChild(script);
(or, preferably, rather than writing the Javascript inline like that, attach a src to the script tag instead, which contains the same content)

Writing french characters to CSV file with CasperJS, but not displayed correctly

I'm using CasperJS, but none of this has to do with the web scraping part.
I'm printing a string (containing french characters) to a csv. When I later open that csv file, all of the french characters don't display correctly.
var fs = require('fs');
var content = 'ë,è,é';
var path = 'target.csv';
fs.write(path, content, 'w');
This ends up being written as �
Is there any way, in the JS script, I can change the encoding of the CSV? I know about the notepad save-as trick but it needs to be automated. If not, is it possible to do through command line?

Excel (at least my version) needs the Byte Order Mark to properly display UTF-8 content from a CSV file. You can achieve this by prepending the content with the \uFEFF unicode character in JavaScript.
Here's the full script in PhantomJS for simplicity (CasperJS works in the same way since it runs in PhantomJS):
var fs = require('fs');
var content = 'ë,è,é';
var path = 'data.csv';
fs.write(path, "\uFEFF" + content, 'w');
phantom.exit();
Make sure that the script file itself is also UTF-8 encoded.

Unzipping files

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)