Motivation: I want to make a browser-based hashing utility so users can compute file hashes without installing software.
The approach I'm considering is a static page with "a file upload button" (except no upload takes place): the user picks a file, and the script computes and displays its hash.
So let's say we have this element on the page:
<input id="file-hasher" type="file" />
This creates a button that allows the users of the web page to select a file via an OS "File open..." dialog in the browser.
Let's say the user clicks said button, selects a file in the dialog, then clicks the "Ok" button to close the dialog.
The selected file name is now stored in:
document.getElementById("file-hasher").value
Here, I'm hoping to use a library like https://github.com/bitwiseshiftleft/sjcl/ to compute the hash of the chosen file. Is there a way to do this or does the browser's security model get in the way?
Yes, you can select a file using the file element, and take a hash of the file locally, 'in-browser', using javascript. The browser's security model does not prevent this; and the hash function from the native Web Crypto API can be used, so there is no need for any external crypto libraries.
Here is a working example:
function hashfile() {
readbinaryfile(fileselector.files[0])
.then(function(result) {
result = new Uint8Array(result);
return window.crypto.subtle.digest('SHA-256', result);
}).then(function(result) {
result = new Uint8Array(result);
var resulthex = Uint8ArrayToHexString(result);
divresult.innerText = 'result: ' + resulthex;
});
}
function readbinaryfile(file) {
return new Promise((resolve, reject) => {
var fr = new FileReader();
fr.onload = () => {
resolve(fr.result)
};
fr.readAsArrayBuffer(file);
});
}
function Uint8ArrayToHexString(ui8array) {
var hexstring = '',
h;
for (var i = 0; i < ui8array.length; i++) {
h = ui8array[i].toString(16);
if (h.length == 1) {
h = '0' + h;
}
hexstring += h;
}
var p = Math.pow(2, Math.ceil(Math.log2(hexstring.length)));
hexstring = hexstring.padStart(p, '0');
return hexstring;
}
<h2>File Hash</h2>
<div>
Select file to take hash of:
<br/>
<input type="file" id="fileselector" onchange="javascript:hashfile();">
</div>
<br/>
<div id="divresult"></div>
The standard browser security model allows you to have the user pick a file and do what you will with it. I'm an older guy and thought surely this kinda mingling with a user's parts would require additional hoops/consent. So #ceving 's answer was best: "Do it and you will see."
Here's a link to a good article: https://humanwhocodes.com/blog/2012/05/08/working-with-files-in-javascript-part-1/
Apologies for not trying first before posting.
Id like to implement a UI where the user selects an image and that image is instantly displayed back to them for review. The user would have to click "submit" to upload/save the image to their profile.
I am having issues with the "instantly display back to the user part".
I am using angular FormData with the following markup & controller:
MARKUP
<input id="chooseFile" type="file" file-model="picFile" />
<img src="{{uploadedImage}}" /> <!-- this populates with filename but what is the path?? -->
CONTROLLER
angular.element('#chooseFile').change(function(){
var file = $scope.picFile; // this comes up "undefined" since file is still uploading when this is fired
$scope.uploadedImage = file.name;
});
I have 2 primary issues with the above code (described in comments):
1) In the controller, file comes up undefined obviously because even the smallest file takes >0s to upload while the callback is fired pretty much instantaneously. I got it work using $timeout but thats a bit of a lame hack. How can I have the callback wait until the file is uploaded??
2) The idea is to upload the file and display it in the img tag using Angular's data-binding. This works in that src is populated with the filename, but what is the path of the img. Some temporary location in cache or something?? Obviously I havent set a path to move the file yet.
Any help appreciated!
I also needed this feature, some how I manage to display image instantly.
angular.module('HelloWorldApp', [])
.controller('HelloWorldController', function($scope) {
$scope.uploadavtar = function(files) {
//var fd = new FormData();
//Take the first selected file
//fd.append("file", files[0]);
var imagefile = document.querySelector('#file');
if (imagefile.files && imagefile.files[0]) {
var reader = new FileReader();
reader.onload = function (e) {
$('#temp_image')
.attr('src', e.target.result);
};
reader.readAsDataURL(imagefile.files[0]);
this.imagefile = imagefile.files[0];
}else{
console.log("Image not selected");
}
}
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script>
<div ng-app="HelloWorldApp">
<div ng-controller="HelloWorldController">
<input type="file" id="file" onchange="angular.element(this).scope().uploadavtar(this.files)"/>
</div>
<img src="" id="temp_image" width="100">
<div>
</div>
</div>
I was using laravel + Angularjs so another related post to store image is : https://stackoverflow.com/a/34830307/2815635
I wrote the following code to check whether the uploaded file exists or not using HTML5 file API.
<input type="file" id="myfile">
<button type="button" onclick="addDoc()">Add Document</button>
<p id="DisplayText"></p>
The following JavaScript code has been mapped to it is as follows:
function addDoc() {
var file=document.getElementById("myFile").files[0]; //for input type=file
var reader=new FileReader();
reader.onload = function(e) {}
reader.readAsText(file);
var error = reader.error;
var texte=reader.result;
document.getElementById("DisplayText").innerText=reader.result; /*<p id="DisplayText>*/
}
After browsing a file from local system I tried to delete the "browsed" document form the folder before clicking on addDoc(). After clicking the button I could still see Filereader.result is not null and could display all the content.
Can someone explain on how the Filereader works? Is it that the FileReader gets bound as soon as the file is browsed?
Also can we check whether the system Readonly Attribute with FileReader similar to Java File.canread()?
Could someone suggest on this? I have IE11 to test the code.
FileReader load event sets the .result value asynchronously. To access the .result use load or loadend event.
When a file has been selected at <input type="file"> Choose File or Browse... UI, deleting file at local filesystem should not effect the File object at FileList returned by .files call. See 2.9.2. Transferable objects, 6.7.3 The DataTransfer interface.
4. The Blob Interface and Binary Data
Each Blob must have an internal snapshot state, which
must be initially set to the state of the underlying storage, if any
such underlying storage exists, and must be preserved through
structured clone. Further normative definition of snapshot state can be found for Files.
2.9.8 Monkey patch for Blob and FileList objects
This monkey patch will be removed in due course. See w3c/FileAPI
issue 32.
Blob objects are cloneable objects.
Each Blob object's [[Clone]] internal method, given targetRealm and ignoring memory, must run these steps:
If this is closed, then throw a "DataCloneError" DOMException.
Return a new instance of this in targetRealm, corresponding to
the same underlying data.
FileList objects are cloneable objects.
Each FileList object's [[Clone]] internal method, given
targetRealm and memory, must run these steps:
Let output be a new FileList object in targetRealm.
For each file in this, add ? [StructuredClone][15](_file, targetRealm, memory_) to the end of the list of File objects
of output.
Return output.
Selecting read-only files or folders at webkit and firefox browsers
At chrome, chromium if read-only permission is set for file at local filesystem and user selects file at <input type="file"> element, where FileReader is used to read file, an error is thrown at FileReader, generated from FileReader progress event.
If a Blob URL is set to the same file object, the blob: URL will not return the the read-only file at request to the Blob URL.
Selection of folder where folder permission is set to read-only
Chrome, chromium
At chrome, chromium where webkitdirectory attribute is set and folder is selected with read-only permission FileList .length of event.target.files returned 0; event.target.files.webkitGetAsEntry() is not called, "No file chosen" is rendered at <input type="file"> shadowDOM. When a folder is dropped at <input type="file"> or element where droppable attribute set, the directory .name and .path of the read-only folder is displayed at drop event.dataTransfer.
When user drops file or folder at <textarea> element, where no drop event is attached beforeunload event is called and a prompr is displayed at UI
Do you want to leave this site?
Changes you made may not be saved.
<Stay><Leave> // <buttons>
Firefox
At firefox version 47.0b9 with allowdirs attribute is set at <input type="file"> element, where user clicks "Choose folder.." <input>, the folder .name and .path of the parent folder are accessible at .then() chained to event.target.getFilesAndDirectories(). The files or folders contained within the selected folder are not returned when recursively iterating Directory entries; an an empty string is returned.
If user clicks "Choose file..." <input> and a folder is selected without read-only permission set, when the folder at file manager is clicked, the files in the folder are listed.
Where a folder is selected where read-only permission is set an alert() notification is rendered at UI displaying
Could not read the contents of <directory name>
Permission denied
Bug, security issue
*nix OS
When user drops folder at <textarea> element, where no drop event is attached, the full path to the folder at user filesystem file: protocol is exposed. The paths to the files contained within the folder are not also set as .value; e.g.,
"file:///home/user/Documents/Document/"
When a file is dropped at <textarea> element, where not drop event is attached, the full path to the file at user filesystem is set as .value of <textarea>; that is,
"file:///home/user/Documents/Document/MyFileFullPathDisplayedAtTextAreaValue.txt"
If multiple files are selected and dropped at <textarea> element, all of the full file paths are set as .value of <textarea>, delineated by new line character \n
"file:///home/user/Documents/Document/MyFileFullPathDisplayedAtTextAreaValue1.txt"
"file:///home/user/Documents/Document/MyFileFullPathDisplayedAtTextAreaValue2.txt"
..
Where an XMLHttpRequest() is made for the file path and error is logged at console
NS_ERROR_DOM_BAD_URI: Access to restricted URI denied
When set as .src of an <img> element with .crossOrigin set to "anonymous" the img error event handler is called
At call to window.open() with full path set at first parameter
Error: Access to '"file:///home/user/Documents/Document/MyFileFullPathDisplayedAtTextAreaValue.png"' from script denied
Specification
4.10.5.1.18. File Upload state (type=file)
EXAMPLE 16
For historical reasons, the value IDL attribute prefixes the
file name with the string "C:\fakepath\". Some legacy user agents
actually included the full path (which was a security vulnerability).
As a result of this, obtaining the file name from the value IDL
attribute in a backwards-compatible way is non-trivial.
4.10.5.4. Common <input> element APIs
filename
On getting, it must return the string "C:\fakepath\" followed by the name of the first file in the list of selected
files, if any, or the empty string if the list is empty. On
setting, if the new value is the empty string, it must empty the list
of selected files; otherwise, it must throw an "InvalidStateError"
DOMException.
NOTE: This "fakepath" requirement is a sad accident of history. See the example in the File Upload state section for more
information.
NOTE: Since path components are not permitted in file names in the list of selected files, the "\fakepath\" cannot be mistaken
for a path component.
4.10.5.1.18. File Upload state (type=file)
Path components
When an <input> element’s type attribute is in the File Upload
state, the rules in this section apply.
The <input> element represents a list of selected files,
each file consisting of a file name, a file type, and a file body (the
contents of the file).
File names must not contain path components, even in the case that a
user has selected an entire directory hierarchy or multiple files with
the same name from different directories. Path components, for the
purposes of the File Upload state, are those parts of file names
that are separated by U+005C REVERSE SOLIDUS character () characters.
Bug report https://bugzilla.mozilla.org/show_bug.cgi?id=1311823
Dropping file at <textarea> at data URI
Following comment by Neal Deakin at bug report
I think the steps referred to are:
Open data:text/html,
Drag a file from the desktop to the textarea
I can reproduce this on Linux, but not on Windows or Mac.
The hunch above is correct; Linux is including the data as a url and
plaintext as well.
dropped files at data: prototcol data URI at firefox, and chrome, chromium
data:text/html,<textarea></textarea>
Firefox
The full path name of file or folder set as .value of <textarea>.
Chrome, chromium
Dropping file at data URI having only textarea element at chrome, chromium replaces the data URI with dropped file path at address bar, and loads the dropped file at the same tab, replacing the data URI with the content of the dropped file.
plnkr http://plnkr.co/edit/ZfAGEAiyLLq8rGXD2ShE?p=preview
html, javascript to reproduce issue described above
<!DOCTYPE html>
<html>
<head>
<style>
body {
height: 400px;
}
textarea {
width: 95%;
height: inherit;
}
</style>
<script>
window.onload = function() {
var button = document.querySelector("#myfile + button");
var input = document.getElementById("myfile");
var display = document.getElementById("DisplayText");
var text = null;
function readFullPathToFileOnUserFileSystem(e) {
var path = e.target.value;
console.log(path);
var w = window.open(path, "_blank");
var img = new Image;
img.crossOrigin = "anonymous";
img.onload = function() {
document.body.appendChild(this);
}
img.onerror = function(err) {
console.log("img error", err.message)
}
img.src = path;
var request = new XMLHttpRequest();
request.open("GET", path.trim(), true);
request.onload = function() {
console.log(this.responseText)
}
request.error = function(err) {
console.log(err.message)
}
request.send();
}
display.addEventListener("input", readFullPathToFileOnUserFileSystem);
input.addEventListener("change", addDoc);
input.addEventListener("progress", function(event) {
console.log("progress", event)
});
button.addEventListener("click", handleText)
function addDoc(event) {
var mozResult = [];
function mozReadDirectories(entries, path) {
console.log("dir", entries, path);
return [].reduce.call(entries, function(promise, entry) {
return promise.then(function() {
console.log("entry", entry);
return Promise.resolve(entry.getFilesAndDirectories() || entry)
.then(function(dir) {
console.log("dir getFilesAndDirectories", dir)
return dir
})
})
}, Promise.resolve())
.catch(function(err) {
console.log(err, err.message)
})
.then(function(items) {
console.log("items", items);
var dir = items.filter(function(folder) {
return folder instanceof Directory
});
var files = items.filter(function(file) {
return file instanceof File
});
if (files.length) {
console.log("files:", files, path);
mozResult = mozResult.concat.apply(mozResult, files);
}
if (dir.length) {
console.log(dir, dir[0] instanceof Directory, dir[0]);
return mozReadDirectories(dir, dir[0].path || path);
} else {
if (!dir.length) {
return Promise.resolve(mozResult).then(function(complete) {
return complete
})
}
}
})
.catch(function(err) {
console.log(err)
})
};
console.log("files", event.target.files);
if ("getFilesAndDirectories" in event.target) {
return (event.type === "drop" ? event.dataTransfer : event.target)
.getFilesAndDirectories()
.then(function(dir) {
if (dir[0] instanceof Directory) {
console.log(dir)
return mozReadDirectories(dir, dir[0].path || path)
.then(function(complete) {
console.log("complete:", complete);
event.target.value = null;
});
} else {
if (dir[0] instanceof File && dir[0].size > 0) {
return Promise.resolve(dir)
.then(function(complete) {
console.log("complete:", complete);
})
} else {
if (dir[0].size == 0) {
throw new Error("could not process '" + dir[0].name + "' directory" + " at drop event at firefox, upload folders at 'Choose folder...' input");
}
}
}
}).catch(function(err) {
console.log(err)
})
}
var reader = new FileReader();
reader.onload = function(e) {
text = reader.result;
console.log("FileReader.result", text);
button.removeAttribute("disabled");
}
reader.onerror = function(err) {
console.log(err, err.loaded, err.loaded === 0, file);
button.removeAttribute("disabled");
}
reader.onprogress = function(e) {
console.log(e, e.lengthComputable, e.loaded, e.total);
}
reader.readAsArrayBuffer(file);
}
function handleText() {
// do stuff with `text`: `reader.result` from `addDoc`
display.textContent = text;
button.setAttribute("disabled", "disabled");
// set `text` to `null` if not needed or referenced again
text = null;
}
}
</script>
</head>
<body>
<input type="file" id="myfile" webkitdirectory directory allowdirs>
<button type="button" disabled>Add Document</button>
<br>
<br>
<textarea id="DisplayText"></textarea>
</body>
</html>
plnkr http://plnkr.co/edit/8Ovw3IlYKI8BYsLhzV88?p=preview
You can use change event attached to #myfile element to handle file selection action by user.
Substitute <textarea> element for <p> element to display result of load event from .readAsText() call.
To display .result of FileReader at click at button element, set variable text to reader.result within load event of FileReader at click event at button set .textContent of #DisplayText element to variable referencing previously set reader.result.
<!DOCTYPE html>
<html>
<style>
body {
height: 400px;
}
textarea {
width:95%;
height: inherit;
}
</style>
<head>
<script>
window.onload = function() {
var button = document.querySelector("#myfile + button");
var input = document.getElementById("myfile");
var display = document.getElementById("DisplayText");
var text = null;
input.addEventListener("change", addDoc);
button.addEventListener("click", handleText)
function addDoc(event) {
var file = this.files[0]
var reader = new FileReader();
reader.onload = function(e) {
text = reader.result;
button.removeAttribute("disabled");
}
reader.onerror = function(err) {
console.log(err, err.loaded
, err.loaded === 0
, file);
button.removeAttribute("disabled");
}
reader.readAsText(event.target.files[0]);
}
function handleText() {
// do stuff with `text`: `reader.result` from `addDoc`
display.textContent = text;
button.setAttribute("disabled", "disabled");
// set `text` to `null` if not needed or referenced again
text = null;
}
}
</script>
</head>
<body>
<input type="file" id="myfile" accept="text/*">
<button type="button" disabled>Add Document</button><br><br>
<textarea id="DisplayText"></textarea>
</body>
</html>
The FileReader object lets web applications asynchronously read the contents of files (or raw data buffers) stored on the user's computer, using File or Blob objects to specify the file or data to read.
File objects may be obtained from a FileList object returned as a result of a user selecting files using the element, from a drag and drop operation's DataTransfer object, or from the mozGetAsFile() API on an HTMLCanvasElement.
The readAsText method is used to read the contents of the specified Blob or File. When the read operation is complete, the readyState is changed to DONE, the loadend is triggered, and the result attribute contains the contents of the file as a text string.
Syntax
instanceOfFileReader.readAsText(blob[, encoding]);
Parameters
Blob
The Blob or File from which to read.
encoding Optional
A string specifying the encoding to use for the returned data. By default, UTF-8 is assumed if this parameter is not specified.
For the metadata about a file we can check the File object F such that:
F has a readability state of OPENED.
F refers to the bytes byte sequence.
F.size is set to the number of total bytes in bytes.
F.name is set to n.
F.type is set to t.
Note: The type t of a File is considered a parsable MIME type if the ASCII-encoded string representing the File object's type, when
converted to a byte sequence, does not return undefined for the parse
MIME type algorithm [MIMESNIFF].
F.lastModified is set to d.
See more about browser compatibility and detailed document for FileReader, File and readAsText at MDN, also this W3C draft for FileApi
Use this instead:-
function loadFileAsText()
{
var fileToLoad = document.getElementById("fileToLoad").files[0];
var fileReader = new FileReader();
fileReader.onload = function(fileLoadedEvent)
{
var textFromFileLoaded = fileLoadedEvent.target.result;
document.getElementById("inputTextToSave").innerText = textFromFileLoaded;
};
fileReader.readAsText(fileToLoad, "UTF-8");
}
<p>Select a File to Load:</p>
<input type="file" id="fileToLoad"><button onclick="loadFileAsText()">Load Selected File</button>
<br>
<br>
<br>
<p>Text file loaded:</p>
<p id="inputTextToSave"></p>
There is the code https://jsfiddle.net/bfzmm1hc/1 Everything looks fine but I want to delete some of the files from the set.
I have already found these:
How to remove one specific selected file from input file control
input type=file multiple, delete items
I know that FileList object is readonly, so I can just copy the files to a new array. But what should I do with this new array of File objects? I can't assign it to the files property...
I found a workaround. This will not require AJAX for the request at all and the form can be sent to the server. Basically you could create an hidden or text input and set it's value attribute to the base64 string created after processing the file selected.
<input type=hidden value=${base64string} />
You will probably consider the idea to create multiple input file instead of input text or hidden. This will not work as we can't assign a value to it.
This method will include the input file in the data sent to the database and to ignore the input file you could:
in the back-end don't consider the field;
you can set the disabled attribute to the input file before serialising the form;
remove the DOM element before sending data.
When you want to delete a file just get the index of the element and remove the input element (text or hidden) from the DOM.
Requirements:
You need to write the logic to convert files in base64 and store all files inside an array whenever the input file trigger the change event.
Pros:
This will basically give you a lot of control and you can filter, comparing files, check for file size, MIME type, and so on..
Since you cannot edit the Read Only input.files attribute, you must upload a form using XMLHttpRequest and send a FormData object. I will also show you how to use URL.createObjectURL to more easily get a URI from the File object:
var SomeCl = {
count: 0,
init: function() {
$('#images').change(this.onInputChange);
},
onInputChange: function() {
// reset preview
$('.container').empty();
// reset count
SomeCl.count = 0;
// process files
SomeCl.processFiles(this.files, function(files) {
// filtered files
console.log(files);
// uncomment this line to upload the filtered files
SomeCl.upload('url', 'POST', $('#upload').get(0), files, 'images[]');
});
},
processFiles: function(files, callback) {
// your filter logic goes here, this is just example
// filtered files
var upload = [];
// limit to first 4 image files
Array.prototype.forEach.call(files, function(file) {
if (file.type.slice(0, 5) === 'image' && upload.length < 4) {
// add file to filter
upload.push(file);
// increment count
SomeCl.count++;
// show preview
SomeCl.preview(file);
}
});
callback(upload);
},
upload: function(method, url, form, files, filename) {
// create a FormData object from the form
var fd = new FormData(form);
// delete the files in the <form> from the FormData
fd.delete(filename);
// add the filtered files instead
fd.append(filename, files);
// demonstrate that the entire form has been attached
for (var key of fd.keys()) {
console.log(key, fd.getAll(key));
}
// use xhr request
var xhr = new XMLHttpRequest();
xhr.open(method, url, true);
xhr.addEventListener('progress', function(e) {
console.log('lengthComputable', e.lengthComputable);
console.log(e.loaded + '/' + e.total);
});
xhr.addEventListener('load', function(e) {
console.log('uploaded');
});
xhr.addEventListener('error', function(e) {
console.log('this is just a demo');
});
xhr.send(fd);
},
preview: function(file) {
// create a temporary URI from the File
var url = URL.createObjectURL(file);
// append a preview
$('.container').append($('<img/>').attr('src', url));
}
};
SomeCl.init();
.container img {
max-width: 250px;
max-height: 250px;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<form id="upload">
<input name="other" type="hidden" value="something else">
<input name="images[]" id="images" multiple="multiple" type="file">
<div class="container"></div>
</form>
For context, I'm trying to create a "click image" file uploader. Initially there is a default image, which I then click. I trigger a file upload, and the user picks an image file they want. Then I will set the image to replace the default (and do other things with it later). Right now, the front end looks something like this:
<div class="right-preview">
<input type="image" src="img/logo.png" height="240px" width="240px" ng-click="uploadImage('right-image')" id="upload-right-image"/>
<input type="file" id="upload-right" style="visibility: hidden">
</div>
When the image is clicked, it triggers an upload action.
$scope.uploadImage = function(side) {
$image = $('#upload-' + side);
$fileInput = $('#upload-right');
$fileInput.change(function(changeEvent) {
var files = changeEvent.target.files;
for(var i = 0; i < files.length; i++) {
file = files[i];
console.log(file);
}
});
$fileInput.trigger('click');
}
When the change event is fired after the user finishes picking their file, I have the changeEvent and I know they've selected their file. Each of the files has some properties (like name and size) but I'm not seeing anything for accessing the raw data so I can set the src on my other element.
Am I just completely missing how to get the image data, or is there a better way to do this? I have no server (right now) to post this to. Perhaps there is a better way to approach this?
This link may be helpful to you - https://developer.mozilla.org/en-US/docs/Web/API/FileReader/readAsDataURL
I took one method from that page and added some additional functionality to hide the file upload button and have the image placeholder trigger its click event.
$('#placeholder').click(function() {
$('#img-upload').trigger('click');
});
function previewFile() {
var preview = document.querySelector('img');
var file = document.querySelector('input[type=file]').files[0];
var reader = new FileReader();
reader.addEventListener("load", function () {
preview.src = reader.result;
}, false);
if (file) {
reader.readAsDataURL(file);
}
}
.hidden {
display: none;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<img width="250" height="250" id="placeholder" src="http://place-hold.it/250x250&text='click to upload'">
<input class="hidden" type="file" onchange="previewFile()" id="img-upload">