I'm trying to read the first byte of the selected file.
But when I select a large file (>100Mb) I get an error: "NotReadableError".
See the code below. Is "array buffer" really a buffer or it just loads the whole stuff into the memory and I MUST use file#slice?
function readFile(file) {
var reader = new FileReader();
reader.onload = function() {
var buffer = reader.result;
var view = new Int8Array(buffer);
try {
view.forEach(function(v, index, array) {
console.log(v);
alert("ok - " + v);
throw "BreakException";
})
} catch (e) {
if (e!=="BreakException") throw e;
}
}
reader.onerror = function() {
alert("error");
console.log(reader.error);
}
reader.readAsArrayBuffer(file);
}
var fileField = document.getElementById("file");
fileField.onchange = function(e) {
var file = e.target.files[0];
readFile(file);
}
<form>
<input id="file" type="file"/>
</form>
An ArrayBuffer is really a buffer, an in-memory buffer. That's how buffers work. Your code tries to load the whole file into memory. To access specific ranges of a file without loading the whole into memory, you must use Blob.slice (Files implement all the methods of Blobs) as you suspected.
$('#file').on('change', function (e) {
if (FileReader) {
var reader = new FileReader();
reader.onload = function (e) {
var data = e.target.result;
};
reader.onloadend = function (x) {
var other = x.target.result;
};
reader.onerror = function (error) {
};
reader.readAsDataURL(e.target.files[0]);
}
});
This is an input of type="file". This works when selecting several file types. But, for some file types e.target.result (including tiff) always comes back null.
e.target.result = null or empty (for some file types)
e.target.error = null.
e.target.readyState = 2.
e.total is always a large positive number.
The result of onloadend is the same as onload and onerror never gets hit.
Please note that this seems to be an IE10 issue. It works fine in IE11, Chrome, and FireFox. My OS is Server 2012.
I'm trying to play the video files from and on client's computer. The thing is it's pretty difficult to get the absolute path so I can put it in video's src or object's data attribute. Eventually I find the FileReader object, and it works on small files pretty well. However, it doesn't fire the onload event when reading large files (200MB+ so far). No error, FileReader.onerror doesn't fire anything, try/catch doesn't help. Developer console doesn't show anything.
I think it has something to do with max file size on each browser's config, but I can't find the way to configure that. Help?
Here's the code
function onclick()
{
var file_dialog = document.getElementById("file_dialog");
var path_dialog = document.getElementById("path_dialog");
var video_player = document.getElementById("video_player");
var begin_video = document.getElementById("begin_video");
var reading_progress = document.getElementById("reading_progress");
file_dialog.onchange = function ()
{
begin_video.disabled = file_dialog.files.length == 0 || path_dialog.files.length == 0;
};
path_dialog.onchange = file_dialog.onchange;
begin_video.onclick = function ()
{
begin_video.disabled = true;
var reader = new FileReader();
reader.onload = function (e)
{
video_player.src = e.target.result;
begin_video.disabled = false;
};
reader.onprogress = function (e)
{
reading_progress.textContent = "Reading... " + (Math.floor(e.loaded / e.total * 10000) / 100) + "%";
};
reader.onloadend = function (e)
{
if (e.target.error != null)
reading_progress.textContent = e.target.error.code;
else
reading_progress.textContent = "FINISHED!!!";
};
reader.onerror = alert;
reader.readAsDataURL(file_dialog.files[0]);
var reader2 = new FileReader();
reader2.onload = function (e)
{
};
};
}
There is no such browser config setting for this.
I've also worked with FileReader and large files (up to 50 MB) and the browsers behave very different:
Chrome => did well and was the most "responsive"
Firefox => did not as well as Chrome, high memory consumption, but worked
IE => worked as long the file was below 15 MB, above the browser just didn't process the file - no feedback, didn't fire any event
Maybe it's a memory issue - tested same files with different machine with less memory and IE denied to work already at 5 MB files.
Hi i am using the JS HTML5 File API to handle file uploads to my server.
I am getting the following error in Aurora(Fire Fox Bleeding edge builds)
NS_ERROR_INVALID_POINTER: Component returned failure code: 0x80004003 (NS_ERROR_INVALID_POINTER) [nsIDOMFileReader.readAsBinaryString]
function readBlob(opt_startByte, opt_stopByte,file,partNo) {
var start = parseInt(opt_startByte);
var stop = parseInt(opt_stopByte);
var reader = new FileReader();
var totalParts = parseInt(file.size/MAX_READ);
if((file.size % MAX_READ) !== 0){
totalParts++;
}
// If we use onloadend, we need to check the readyState.
reader.onloadend = function(evt) {
if (evt.target.readyState == FileReader.DONE) {
//var contents = reader.result;
postFilePart(partNo,contents,totalParts,escape(file.name))// DONE == 2
}
};
if (file.webkitSlice) {
var blob = file.webkitSlice(start, stop);
} else if (file.mozSlice) {
var blob = file.mozSlice(start, stop);
}
reader.readAsBinaryString(blob);
}
the error is occurring at this line
reader.readAsBinaryString(blob);
i have tried mozSlice and Slice
if (file.mozSlice) {
var blob = file.mozSlice(start, stop);
}
and it gave me the same results. it might not be the best idea to use HTML 5 API yet as this may cause issues with other browsers as well.
does anyone have a work around to get the same functionality or how i can resolve this particular error
Solved the issue it it was rerunning the reader code with incorrect parameters due to a mistake on the calling method
https://bugzilla.mozilla.org/show_bug.cgi?id=725289
rather use slice vs mozSlice
I'm attempting to provide a script-only solution for reading the contents of a file on a client machine through a browser.
I have a solution that works with Firefox and Internet Explorer. It's not pretty, but I'm only trying things at the moment:
function getFileContents() {
var fileForUpload = document.forms[0].fileForUpload;
var fileName = fileForUpload.value;
if (fileForUpload.files) {
var fileContents = fileForUpload.files.item(0).getAsBinary();
document.forms[0].fileContents.innerHTML = fileContents;
} else {
// try the IE method
var fileContents = ieReadFile(fileName);
document.forms[0].fileContents.innerHTML = fileContents;
}
}
function ieReadFile(filename)
{
try
{
var fso = new ActiveXObject("Scripting.FileSystemObject");
var fh = fso.OpenTextFile(filename, 1);
var contents = fh.ReadAll();
fh.Close();
return contents;
}
catch (Exception)
{
return "Cannot open file :(";
}
}
I can call getFileContents() and it will write the contents into the fileContents text area.
Is there a way to do this in other browsers?
I'm most concerned with Safari and Chrome at the moment, but I'm open to suggestions for any other browser.
Edit: In response to the question, "Why do you want to do this?":
Basically, I want to hash the file contents together with a one-time-password on the client side so I can send this information back as a verification.
Edited to add information about the File API
Since I originally wrote this answer, the File API has been proposed as a standard and implemented in most browsers (as of IE 10, which added support for FileReader API described here, though not yet the File API). The API is a bit more complicated than the older Mozilla API, as it is designed to support asynchronous reading of files, better support for binary files and decoding of different text encodings. There is some documentation available on the Mozilla Developer Network as well as various examples online. You would use it as follows:
var file = document.getElementById("fileForUpload").files[0];
if (file) {
var reader = new FileReader();
reader.readAsText(file, "UTF-8");
reader.onload = function (evt) {
document.getElementById("fileContents").innerHTML = evt.target.result;
}
reader.onerror = function (evt) {
document.getElementById("fileContents").innerHTML = "error reading file";
}
}
Original answer
There does not appear to be a way to do this in WebKit (thus, Safari and Chrome). The only keys that a File object has are fileName and fileSize. According to the commit message for the File and FileList support, these are inspired by Mozilla's File object, but they appear to support only a subset of the features.
If you would like to change this, you could always send a patch to the WebKit project. Another possibility would be to propose the Mozilla API for inclusion in HTML 5; the WHATWG mailing list is probably the best place to do that. If you do that, then it is much more likely that there will be a cross-browser way to do this, at least in a couple years time. Of course, submitting either a patch or a proposal for inclusion to HTML 5 does mean some work defending the idea, but the fact that Firefox already implements it gives you something to start with.
In order to read a file chosen by the user, using a file open dialog, you can use the <input type="file"> tag. You can find information on it from MSDN. When the file is chosen you can use the FileReader API to read the contents.
function onFileLoad(elementId, event) {
document.getElementById(elementId).innerText = event.target.result;
}
function onChooseFile(event, onLoadFileHandler) {
if (typeof window.FileReader !== 'function')
throw ("The file API isn't supported on this browser.");
let input = event.target;
if (!input)
throw ("The browser does not properly implement the event object");
if (!input.files)
throw ("This browser does not support the `files` property of the file input.");
if (!input.files[0])
return undefined;
let file = input.files[0];
let fr = new FileReader();
fr.onload = onLoadFileHandler;
fr.readAsText(file);
}
<input type='file' onchange='onChooseFile(event, onFileLoad.bind(this, "contents"))' />
<p id="contents"></p>
There's a modern native alternative: File implements Blob, so we can call Blob.text().
async function readText(event) {
const file = event.target.files.item(0)
const text = await file.text();
document.getElementById("output").innerText = text
}
<input type="file" onchange="readText(event)" />
<pre id="output"></pre>
Currently (September 2020) this is supported in Chrome and Firefox, for other Browser you need to load a polyfill, e.g. blob-polyfill.
Happy coding!
If you get an error on Internet Explorer, Change the security settings to allow ActiveX
var CallBackFunction = function(content) {
alert(content);
}
ReadFileAllBrowsers(document.getElementById("file_upload"), CallBackFunction);
//Tested in Mozilla Firefox browser, Chrome
function ReadFileAllBrowsers(FileElement, CallBackFunction) {
try {
var file = FileElement.files[0];
var contents_ = "";
if (file) {
var reader = new FileReader();
reader.readAsText(file, "UTF-8");
reader.onload = function(evt) {
CallBackFunction(evt.target.result);
}
reader.onerror = function(evt) {
alert("Error reading file");
}
}
} catch (Exception) {
var fall_back = ieReadFile(FileElement.value);
if (fall_back != false) {
CallBackFunction(fall_back);
}
}
}
///Reading files with Internet Explorer
function ieReadFile(filename) {
try {
var fso = new ActiveXObject("Scripting.FileSystemObject");
var fh = fso.OpenTextFile(filename, 1);
var contents = fh.ReadAll();
fh.Close();
return contents;
} catch (Exception) {
alert(Exception);
return false;
}
}
This works fine
function onClick(event) {
filecontent = "";
var myFile = event.files[0];
var reader = new FileReader();
reader.addEventListener('load', function (e) {
filecontent = e.target.result;
});
reader.readAsBinaryString(myFile);
}