I haven't found any mentions in the HTML spec nor anywhere on the web, that says this is possible, still I ask just in case.
Is it possible to get the URL of a module to for example fetch files relative to that URL?
Let's say my index.html has a:
<script type="module">import '/foo/foo.js'</script>
and foo.js wants to know what it's own url is to load dynamically some file e.g. ./file-inside-foo.
As of the time of this writing document.currentScript returns null inside modules and is probably like that by design?
ECMA-262 has a Stage 3 Proposal for implementing import.meta. On the web this exposes a property named url that, when accessed from within a module, gives access to the full URL of that module.
// in /path/to/your/module.js
const { pathname } = new URL(import.meta.url);
console.log(pathname); // '/path/to/your/module.js'
You can also use the second parameter of the URL constructor to skip a step here:
const url = new URL('relative/file.js', import.meta.url);
Unfortunately, import.meta may not be available in all browsers yet but was implemented in v64 of Google Chrome.
The HTML Living Standard currently includes a Stage 3 Proposal to the ECMA-262 Standard that implements import.meta which exposes a property named url providing the full path to the current module including the protocol and filename.
// import.meta.url == 'http://your.domain.name/path/to/your/module.js'
To get the path of the current module without the protocol + domain you can construct a URL object from this value and access its .pathname property:
const modulePath = new URL(import.meta.url).pathname;
// modulePath = '/path/to/your/module.js'
To determine the directory where the current module is located you would construct a URL object for the relative path ./ using import.meta.url as the base parameter:
const moduleDir = new URL('./', import.meta.url).pathname;
// moduleDir == '/path/to/your/'
You can also get the path of any file relative to the current module in the same manner. For example:
let img = new Image();
image.src = new URL('../icons/glyph.png', import.meta.url).pathname;
// image.src == '/path/to/icons/glyph.png'
Unfortunately import.meta may not be available in all browsers yet however it was implemented in v64 of Google Chrome.
Related
I am trying to call an API, loop through an array of images, assign unique names to each image in the array and then write them to a local directory. If I simplify the code I can write them to the root folder .I already created the sub folder manually, so it existed prior to running the function.
Here is my basic function:
const imageFolder = './img';
function downloadImage(url, filepath) {
client.get(url, res => {
res.pipe(fs.createWriteStream(`${imageFolder}/${filepath}`));
});
}
...make api call
const imagesArray = generations.data.map(item => item.generation.image_path);
imagesArray.forEach(item => {
// const fileName = uuid.v4() + '.webp'; // trying to assign unique filename with uuid
const fileName = new Date().getTime().toString() + '.webp'; // trying to assign unique filename with date object
downloadImage(item, fileName);
});
If I change
res.pipe(fs.createWriteStream(`${imageFolder}/${filepath}`));
to
res.pipe(fs.createWriteStream(filepath));
then it will work but just dumps the images in the root. I was thinking perhaps I was trying to concatenate a variable name with a string (for fileName + '.webp', but it is working in the root as mentioned. See attached image.
I also tried adding the path into the actual function call inside the forEach loop like so
downloadImage(item, `${imageFolder}/${fileName}`);
I did wonder about needing the __dirname variable, or whether it could be a permissions issue, but I don't see any errors.
I am assuming this is pretty straightforward.
OK, was fairly simple and I guess I sort of knew it once I got it working, changing to
downloadImage(item, path.join('src', 'img', fileName));
path.join concatenates folder names and fixes issues when working across platforms (OSX, Windows etc) which applies in this case as I am testing from both Windows and Mac.
This question already has answers here:
Check if file has changed using HTML5 File API
(3 answers)
Closed 2 years ago.
I have a web app, where the user can select a local file as input, using the html5 FileReader API. Is there any way I can check if the file has changed, that works in modern browsers?
Historically, this was possible in some browsers by polling the file object and comparing the File.lastModifiedDate (deprecated) or File.lastModified property, as outlined in this QA: Check if file has changed using HTML5 File API. However, the spec says that lastModifiedDate and other file data should be a snapshot of the file as it looked like when the users first selected it, so this should not work (and it seems like recent versions of most browsers indeed follow the spec now, making this hack unavailable).
I was hoping to be able to check for changes by reading the file. This kind of works, but as soon as the file is changed on disk, Chrome and Firefox throw an error saying DOMException: The requested file could not be read, typically due to permission problems that have occurred after a reference to a file was acquired. Is there any way around this?
This is what I tried:
let oldText
setInterval(function () {
const fileObj = document.getElementById('myFileInput').files[0]
const reader = new FileReader()
reader.onload = evt => {
const text = evt.target.result
if (text !== oldText) {
console.log("The file has changed!")
oldText = text
}
}
reader.readAsText(fileObj)
}, 1000)
...or simpler:
const fileObj = document.getElementById('myFileInput').files[0]
const reader = new FileReader()
reader.readAsText(fileObj) // works
// now lets edit the file and try again
reader.readAsText(fileObj) // fails
reader.readAsText() works as expected, until the file is changed, when it throws the error mentioned above. I guess this is a security measure of sorts, though I don't fully understand what it's trying to protect the user from. What can I do instead?
This will be possible again if/when the Native File System API is implemented in browsers. It will be partially enabled in Google Chrome 85, scheduled for release in October 2020.
Unlike the FileReader API it requires a explicit user interaction, so you'd do something like this:
myFileInput.addEventListener('change', async (e) => {
const fh = await window.chooseFileSystemEntries()
// fh is now a FileSystemFileHandle object
// Use fh.getFile() to get a File object
})
In my Vue app I receive a PDF as a blob, and want to display it using the browser's PDF viewer.
I convert it to a file, and generate an object url:
const blobFile = new File([blob], `my-file-name.pdf`, { type: 'application/pdf' })
this.invoiceUrl = window.URL.createObjectURL(blobFile)
Then I display it by setting that URL as the data attribute of an object element.
<object
:data="invoiceUrl"
type="application/pdf"
width="100%"
style="height: 100vh;">
</object>
The browser then displays the PDF using the PDF viewer. However, in Chrome, the file name that I provide (here, my-file-name.pdf) is not used: I see a hash in the title bar of the PDF viewer, and when I download the file using either 'right click -> Save as...' or the viewer's controls, it saves the file with the blob's hash (cda675a6-10af-42f3-aa68-8795aa8c377d or similar).
The viewer and file name work as I'd hoped in Firefox; it's only Chrome in which the file name is not used.
Is there any way, using native Javascript (including ES6, but no 3rd party dependencies other than Vue), to set the filename for a blob / object element in Chrome?
[edit] If it helps, the response has the following relevant headers:
Content-Type: application/pdf; charset=utf-8
Transfer-Encoding: chunked
Content-Disposition: attachment; filename*=utf-8''Invoice%2016246.pdf;
Content-Description: File Transfer
Content-Encoding: gzip
Chrome's extension seems to rely on the resource name set in the URI, i.e the file.ext in protocol://domain/path/file.ext.
So if your original URI contains that filename, the easiest might be to simply make your <object>'s data to the URI you fetched the pdf from directly, instead of going the Blob's way.
Now, there are cases it can't be done, and for these, there is a convoluted way, which might not work in future versions of Chrome, and probably not in other browsers, requiring to set up a Service Worker.
As we first said, Chrome parses the URI in search of a filename, so what we have to do, is to have an URI, with this filename, pointing to our blob:// URI.
To do so, we can use the Cache API, store our File as Request in there using our URL, and then retrieve that File from the Cache in the ServiceWorker.
Or in code,
From the main page
// register our ServiceWorker
navigator.serviceWorker.register('/sw.js')
.then(...
...
async function displayRenamedPDF(file, filename) {
// we use an hard-coded fake path
// to not interfere with legit requests
const reg_path = "/name-forcer/";
const url = reg_path + filename;
// store our File in the Cache
const store = await caches.open( "name-forcer" );
await store.put( url, new Response( file ) );
const frame = document.createElement( "iframe" );
frame.width = 400
frame.height = 500;
document.body.append( frame );
// makes the request to the File we just cached
frame.src = url;
// not needed anymore
frame.onload = (evt) => store.delete( url );
}
In the ServiceWorker sw.js
self.addEventListener('fetch', (event) => {
event.respondWith( (async () => {
const store = await caches.open("name-forcer");
const req = event.request;
const cached = await store.match( req );
return cached || fetch( req );
})() );
});
Live example (source)
Edit: This actually doesn't work in Chrome...
While it does set correctly the filename in the dialog, they seem to be unable to retrieve the file when saving it to the disk...
They don't seem to perform a Network request (and thus our SW isn't catching anything), and I don't really know where to look now.
Still this may be a good ground for future work on this.
And an other solution, I didn't took the time to check by myself, would be to run your own pdf viewer.
Mozilla has made its js based plugin pdf.js available, so from there we should be able to set the filename (even though once again I didn't dug there yet).
And as final note, Firefox is able to use the name property of a File Object a blobURI points to.
So even though it's not what OP asked for, in FF all it requires is
const file = new File([blob], filename);
const url = URL.createObjectURL(file);
object.data = url;
In Chrome, the filename is derived from the URL, so as long as you are using a blob URL, the short answer is "No, you cannot set the filename of a PDF object displayed in Chrome." You have no control over the UUID assigned to the blob URL and no way to override that as the name of the page using the object element. It is possible that inside the PDF a title is specified, and that will appear in the PDF viewer as the document name, but you still get the hash name when downloading.
This appears to be a security precaution, but I cannot say for sure.
Of course, if you have control over the URL, you can easily set the PDF filename by changing the URL.
I believe Kaiido's answer expresses, briefly, the best solution here:
"if your original URI contains that filename, the easiest might be to simply make your object's data to the URI you fetched the pdf from directly"
Especially for those coming from this similar question, it would have helped me to have more description of a specific implementation (working for pdfs) that allows the best user experience, especially when serving files that are generated on the fly.
The trick here is using a two-step process that perfectly mimics a normal link or button click. The client must (step 1) request the file be generated and stored server-side long enough for the client to (step 2) request the file itself. This requires you have some mechanism supporting unique identification of the file on disk or in a cache.
Without this process, the user will just see a blank tab while file-generation is in-progress and if it fails, then they'll just get the browser's ERR_TIMED_OUT page. Even if it succeeds, they'll have a hash in the title bar of the PDF viewer tab, and the save dialog will have the same hash as the suggested filename.
Here's the play-by-play to do better:
You can use an anchor tag or a button for the "download" or "view in browser" elements
Step 1 of 2 on the client: that element's click event can make a request for the file to be generated only (not transmitted).
Step 1 of 2 on the server: generate the file and hold on to it. Return only the filename to the client.
Step 2 of 2 on the client:
If viewing the file in the browser, use the filename returned from the generate request to then invoke window.open('view_file/<filename>?fileId=1'). That is the only way to indirectly control the name of the file as shown in the tab title and in any subsequent save dialog.
If downloading, just invoke window.open('download_file?fileId=1').
Step 2 of 2 on the server:
view_file(filename, fileId) handler just needs to serve the file using the fileId and ignore the filename parameter. In .NET, you can use a FileContentResult like File(bytes, contentType);
download_file(fileId) must set the filename via the Content-Disposition header as shown here. In .NET, that's return File(bytes, contentType, desiredFilename);
client-side download example:
download_link_clicked() {
// show spinner
ajaxGet(generate_file_url,
{},
(response) => {
// success!
// the server-side is responsible for setting the name
// of the file when it is being downloaded
window.open('download_file?fileId=1', "_blank");
// hide spinner
},
() => { // failure
// hide spinner
// proglem, notify pattern
},
null
);
client-side view example:
view_link_clicked() {
// show spinner
ajaxGet(generate_file_url,
{},
(response) => {
// success!
let filename = response.filename;
// simplest, reliable method I know of for controlling
// the filename of the PDF when viewed in the browser
window.open('view_file/'+filename+'?fileId=1')
// hide spinner
},
() => { // failure
// hide spinner
// proglem, notify pattern
},
null
);
I'm using the library pdf-lib, you can click here to learn more about the library.
I solved part of this problem by using api Document.setTitle("Some title text you want"),
Browser displayed my title correctly, but when click the download button, file name is still previous UUID. Perhaps there is other api in the library that allows you to modify download file name.
At the moment, due to the security policy Chromium can not read local files via ajax without --allow-file-access-from-files. But I currently need to create a web application where the database is a xml-file (in the extreme case, json), located in one dir with index.html. It is understood that the user can run this application locally. Are there workarounds for reading xml- (json-) file, without wrapping it in a function and change to js extension?
loadXMLFile('./file.xml').then(xml => {
// working with xml
});
function loadXMLFile(filename) {
return new Promise(function(resolve, reject) {
if('ActiveXObject' in window) {
// If is IE
var xmlDoc = new ActiveXObject('Microsoft.XMLDOM');
xmlDoc.async = false;
xmlDoc.load(filename);
resolve(xmlDoc.xml);
} else {
/*
* how to read xml file if is not IE?
* ...
* resolve(something);
*/
}
}
}
Accessing file: protocol at chromium using XMLHttpRequest() or <link> element without --allow-file-access-from-files flag set at chromium instance launch is not enabled by default.
--allow-file-access-from-files
By default, file:// URIs cannot read other file:// URIs. This is an
override for developers who need the old behavior for testing.
At the moment, due to the security policy Chromium can not read local
files via ajax without --allow-file-access-from-files. But I
currently need to create a web application where the database is a
xml-file (in the extreme case, json), located in one dir with
index.html. It is understood that the user can run this application
locally. Are there workarounds for reading xml- (json-) file, without
wrapping it in a function and change to js extension?
If user is aware that local files are to be used by the application you can utilize <input type="file"> element for user to upload file from user local filesystem, process file using FileReader, then proceed with application.
Else, advise user that use of application requires launching chromium with --allow-file-access-from-files flag set, which can be done by creating a launcher for this purpose, specifying a different user data directory for the instance of chromium. The launcher could be, for example
/usr/bin/chromium-browser --user-data-dir="/home/user/.config/chromium-temp" --allow-file-access-from-files
See also How do I make the Google Chrome flag “--allow-file-access-from-files” permanent?
The above command could also be run at terminal
$ /usr/bin/chromium-browser --user-data-dir="/home/user/.config/chromium-temp" --allow-file-access-from-files
without creating a desktop launcher; where when the instance of chromium is closed run
$ rm -rf /home/user/.config/chromium-temp
to remove the configuration folder for the instance of chromium.
Once the flag is set, user can include <link> element with rel="import" attribute and href pointing to local file and type set to "application/xml", for option other than XMLHttpRequest to get file. Access XML document using
const doc = document.querySelector("link[rel=import]").import;
See Is there a way to know if a link/script is still pending or has it failed.
Another alternative, though more involved, would be to use requestFileSystem to to store the file at LocalFileSystem.
See
How to use webkitRequestFileSystem at file: protocol
jQuery File Upload Plugin: Is possible to preserve the structure of uploaded folders?
How to Write in file (user directory) using JavaScript?
Or create or modify a chrome app and use
chrome.fileSystem
See GoogleChrome/chrome-app-samples/filesystem-access.
The simplest approach would be to provide a means for file upload by affirmative user action; process the uploaded file, then proceed with the application.
const reader = new FileReader;
const parser = new DOMParser;
const startApp = function startApp(xml) {
return Promise.resolve(xml || doc)
};
const fileUpload = document.getElementById("fileupload");
const label = document.querySelector("label[for=fileupload]");
const handleAppStart = function handleStartApp(xml) {
console.log("xml document:", xml);
label.innerHTML = currentFileName + " successfully uploaded";
// do app stuff
}
const handleError = function handleError(err) {
console.error(err)
}
let doc;
let currentFileName;
reader.addEventListener("loadend", handleFileRead);
reader.addEventListener("error", handleError);
function handleFileRead(event) {
label.innerHTML = "";
currentFileName = "";
try {
doc = parser.parseFromString(reader.result, "application/xml");
fileUpload.value = "";
startApp(doc)
.then(function(data) {
handleAppStart(data)
})
.catch(handleError);
} catch (e) {
handleError(e);
}
}
function handleFileUpload(event) {
let file = fileUpload.files[0];
if (/xml/.test(file.type)) {
reader.readAsText(file);
currentFileName = file.name;
}
}
fileUpload.addEventListener("change", handleFileUpload)
<input type="file" name="fileupload" id="fileupload" accept=".xml" />
<label for="fileupload"></label>
use document.implementation.createDocument("", "", null)
instead of new ActiveXObject('Microsoft.XMLDOM').
You can find the API through GOOGLE. Good luck.
If I understand correctly, the deliverable is intended to run locally so you will not be able to set any flags for local file access on a user's machine. Something I've done in a pinch is to pack it up as an executable with something like nw.js and keep the external data files. Otherwise, you're probably looking at loading as script using a JSON schema in a JS file.
I had a similar problem before. I solved by simply embedding the XML file into the HTML using PHP. Since the application is loaded locally from disk, size, cache etc. are not a concern.
If you're using Webpack, you can instead directly import the file using a loader like this or this, in which case the file is included into the resulting bundled javascript.
You can load XML through a string of text using DOMParser, Just load your file and parse the text using the .parseFromString. You could use an if statement containing (window.DOMParser) to check if the DOMParser is supported
I have a script at http://localhost/js/foo.js which needs to spawn a Web Worker from the file http://localhost/js/fooWorker.js. I assumed I could just do something like this:
var worker = new Worker('fooWorker.js')
However, this results in a 404 error, as the browser cannot find http://localhost/fooWorker.js. I was under the impression that worker paths were resolved relative to the script spawning the worker, so shouldn't I just be able to specify the name of another .js file in the same directory without having to provide an absolute path? Am I doing something wrong?
From http://www.w3.org/TR/workers/:
When the Worker(scriptURL) constructor is invoked, the user agent must
run the following steps:
Resolve the scriptURL argument relative to the entry script's base
URL, when the method is invoked.
Actually, it should be relative to the embedded document path
For example,
I have
pathDoc\docA.html
js\b.js
js\worker\c.js
then code should be
var worker = new Worker('..\js\worker\c.js')
Note, you can still get the script url within the worker using the self.location and just prepend it to the paths to make them relative from the worker script rather than html base url.
const workerUrl = location + '';
const basePath = workerUrl.replace(/\/[^/]+$/, '/');
self.importScripts(basePath + '/fooWorker.js');
Btw, if you include your worker via blob, you can still pass meta info like it's url via # hash params.
With import.meta.url, you should be able to have it work like relative path.
var worker = new Worker(new URL('./fooWorker.js', import.meta.url));