Simulate XHR2 file upload - javascript

I have a HTML upload button to send (multiple) files to a server which responds with JSON. Based on that response, my application flow continues.
Now, to test the rest of my code (dependent on the server response), I would like to simulate the file upload so that I do not have to manually select and upload new files on every reload.
Following is a simplified version of my upload method:
uploadToServer: function (file) {
var self = this,
data = new FormData(),
xhr = new XMLHttpRequest();
// When the request has successfully completed.
xhr.onload = function () {
var response = $.parseJSON(this.responseText);
var photo = new App.Models.Photo({
filename: response.filename,
name: response.uuid
});
var photoView = new App.Views.Photo({ model: photo });
$('.photos').append(photoView.render().el);
};
// Send to server, where we can then access it with $_FILES['file].
data.append('file', file);
xhr.open('POST', this.url);
xhr.send(data);
}
The uploadToServer parameter file is a File-object from FileList. And as you can see, my server awaits the file inside of $_FILES['file'].
It would be awesome if a could simulate a real File-object being passed into uploadToServer, since I then do not have to worry about my existing events such as xhr.onload and xhr.onprogress being available.
If that won't be possible, I could create a custom uploadToServer method and send a regular AJAX-request and fake-respond on my server. But how can I then use and bind the code from my events (xhr.onload, xhr.onprogress etc.) to that AJAX-request?

You could simulate a file upload by creating a canvas, converting it to a file and passing the result to your method.
Create a canvas : here, a nice red square
var canvas = document.createElement('canvas'),
ctx = canvas.getContext("2d");
canvas.width = 100;
canvas.height = 100;
ctx.fillStyle = '#ff0000';
ctx.fillRect(0, 0, 100, 100);
document.body.appendChild(canvas);
Convert it to a file and pass it to your method: I used Canvas to Blob to simplify the test but you probably can extract the bare bones to fit your needs.
canvas.toBlob( function (blob) {
m.uploadToServer(blob);
}, 'image/jpeg');
And a Fiddle http://jsfiddle.net/pvWxx/ Be sure to open a console to see the events and the request.
If you want to pass a filename with your blob, you can pass a third argument to formData.append, see How to give a Blob uploaded as FormData a file name? and an updated Fiddle http://jsfiddle.net/pvWxx/1/

Related

Using Simple Webaudiorecorder.js in R/Shiny and posting the recording to the server

I am using WebAudioRecorder.js for making online recordings in an R Shiny app, see:
https://github.com/addpipe/simple-web-audio-recorder-demo
As a format, I chose the wave format, and in the JavaScript code, the recording is obtained as a blob. I would like the program to save this blob on the server without any dialog.
Here, you shouldn't set the hole filePath in javascript, you should give it a filename and then php should put it in the correct folder.
function uploadWaveBlob (blob, encoding) {
var xhr = new XMLHttpRequest();
var formData = new FormData();
var fileName = Date().toISOString() + '.' + encoding;
formData.append("Wav", blob, fileName);
xhr.open('POST', uploadUrl);
xhr.onload = function () {
console.log('xhr complete');
};
xhr.send(formData);
}
imagine if i would upload something to like /etc/hosts or something
The following site gives code that shows how to upload a blob to the server:
https://gist.github.com/primaryobjects/d6cdf5d31242a629b0e4cda1bfc4bff9
The complete solution is available at:
https://github.com/heeringa0/simple-web-audio-recorder
and shows how to integrate the Simple WebAudioRecorder.js in an R Shiny app where the recording is saved to the server.

Override Javascript Blob implementation for XHR upload

Supposing I want to upload a stream of random data from my browser to a remote server. I would use something like
var oReq = new XMLHttpRequest();
oReq.open("POST", url, true);
oReq.onload = function (oEvent) {
// Uploaded.
};
var blob = new Blob(['abc123'], {type: 'text/plain'});
oReq.send(blob);
and repeat this as many times as I have chunks to upload.
But, what if I wanted to send it using a single XHR request ? Is it possible to override the Blob function and do something like
function Blob(arr, options) {
var chunkSize = 1024;
MyBlob.prototype.nextChunk(function () {
return arr.splice(0, chunkSize);
});
}
I know that nextChunk does not exist, obviously, but maybe there is some interface that can be overridden ? I looked at the Blob specification and I tried using an alternative Blob implementation (that I modified slightly to force overriding window.Blob), but nothing was sent to the server.

JavaScript FileReader Massive Result

I've got a FileReader that lets the user upload a file (image) to my site.
Here's the code that does the reading:
$("input[type='file']").change(function(e) {
var buttonClicked = $(this);
for (var i = 0; i < e.originalEvent.srcElement.files.length; i++) {
var file = e.originalEvent.srcElement.files[i];
var img = document.createElement("img");
var reader = new FileReader();
reader.onloadend = function() {
img.src = reader.result;
console.log(reader.result);
}
reader.readAsDataURL(file);
}
});
All is good and well, until I tried to print out my result. I used this file for example:
When I console.log() the result, it spits out over 95000 characters.
This image in particular is around the same size as the images I will be accepting into my site.
I was hoping to store these images in a database as well, and so I'm wondering how this is going to be possible with image sources that are so extremely long. Is there a way to shorten this or get the image path a different way?
I'm moreso curious as to why they're so long, but if someone has a tip to store these (100s per user, 500+ users) that'd be nice as well!
Thanks-
Store the Files as ... Files.
There are very little use cases where you need the toDataURL() method of the FileReader, so every time you use it, you should ask yourself why you need it.
In your case :
To display the image in the page. Well don't use a FileReader for this, instead create a direct pointer to the file in the form of an url, available only to this session. This can be achieved with the URL.createObjectURL(File_orBlob) method.
To store this image on your server. Don't store a ~37% bigger base64 version, send and store directly the file as a file (multipart). This can be achieved easily with the FormData API.
inp.onchange = function(){
var file = this.files[0];
if(file.type.indexOf('image/') !== 0){
console.warn('not an image');
}
var img = new Image();
img.src = URL.createObjectURL(file);
// this is not needed in this case but still a good habit
img.onload = function(){
URL.revokeObjectURL(this.src);
};
document.body.appendChild(img);
}
// not active but to give you da codez
function sendToServer(){
var file = inp.files[0];
var form = new FormData();
// here 'image' is the parameter name where you'll retrieve the file from in the request
form.append('image', file);
form.append('otherInfo', 'some other infos');
var xhr = new XMLHttpRequest();
xhr.open('post', 'yourServer/uploadPage')
xhr.onload = function(){
console.log('saved');
};
xhr.send(form);
}
<input type="file" id="inp">
And if you need PHP code to retrieve the File form this request :
if ( isset( $_FILES["image"] ) ){
$dir = 'some/dir/';
$blob = file_get_contents($_FILES["image"]['tmp_name']);
file_put_contents($dir.$_FILES["image"]["name"], $blob);
}
You're going to want to upload the files to a server of some sort (a backend that is serving up your javascript), and then from there you'll want to
Validate the file
Store the file on a physical server (or the cloud) somewhere
Add an entry in a database that relates the file path or ID of that upload to the user who just uploaded it (so you can retrieve it later if needed)
So basically, you don't store the image in your database, you store it on a file share/cloud host somewhere, and instead you only store what is needed to download/retrieve the image later.

javascript - getting object HTMLImageElement instead of base64 string

This is a continuation to my previous question but the issue is new and the solution from that question didn't help. This is a new question.
Here's the link to my previous question where I asked how to convert canvas to an image: javascript- unable to convert canvas to image data
And I'm hoping to get the base64 encoded string of the image which I can send to a PHP service via AJAX call and PHP service is gonna convert it to image and move it to a specified directory.
Function that converts canvas to image
function convertCanvasToImage(canvas)
{
var image = new Image();
image.src = canvas.toDataURL("image/png");
return image;
}
This is the form I created:
var url = 'url to php service';
var file = dataURL; //this is the image url that i'm sending
console.log(file);
var formdata = new FormData();
formdata.append("base64image", file);
formdata.append('csrf_test_name',csrf_token);
var ajax = new XMLHttpRequest();
ajax.addEventListener("load", function(event) {
uploadcomplete(event);
}, false);
ajax.open("POST", url);
ajax.send(formdata);
I tried console.log() the image that canvas returned and this is what I obtained:
<img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAoAAAAHgCAYAAAA10dzkAAAgAElEQVR4nGzbZ3Mba5au6fqvJ2JiTs/pPtVV20j0sOm9T3iARqI3IOi9SIoGHqATJe29q/v8jXs+QMWeHT0fnkgGyUgCiRfIi2ut9y9OqYGZ3yKqHWHlttFiCz1nE8Q+XuDiuSb5XEBccYgrDv6si5ZTMOZMzHkLMS6gFspI8TxiOEfkfCS0P1AM1lmcPaJYPcbyNvDDHUqVU5zdTaS1j4hFm3Erg5bxCK0KxXiWUm6OcLaAW46xCzZBNcAOF3FzK8TBIoG7QC7v4AUalqdRquVQZxeQa/PYc2vYc2uUnWUCuYovR+TMEoEVY8oOnhES2jlKVo2au0DZXiVSF/DciDDMUyjOEuerGGqJYm6VaG6DhBahOyW8eB4rrBGVl5BmZ5FmZ1HyLlrJZ37ep1jUyXseOdel7FWpBrMUgwXy3ixGJGLlZLRIxipoh...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">
It has image tag. Maybe it's because of that; when I pass it to PHP service, it's not able to convert it. This is what it returned me when I debugged
object HTMLImageElement
I tried to convert the above mentioned image tag to base64 using a function like given below but it failed.
function encodeImageFileAsURL(cb) {
return function(){
var file = this.files[0];
var reader = new FileReader();
reader.onloadend = function () {
cb(reader.result);
}
reader.readAsDataURL(file);
}
}
Can anyone help me understand what i am missing here? Thanks a lot!
Reference:
https://davidwalsh.name/browser-camera
https://davidwalsh.name/convert-canvas-image
You already have a data URI at the src of the <img> element at variable image. Pass the value of the src of the <img> element to php, not the html <img> element.
var file = image.src; //this is the image url that i'm sending

JS: how can I base64 encode a local file without XMLHttpRequest?

I'm trying to base64 encode a local file. It's next to my .js file so there's no uploading going on. Solutions like this (using XMLHttpRequest) get a cross-site scripting error.
I'm trying something like this (which doesn't work but it might help explain my problem):
var file = 'file.jpg'
var reader = new FileReader();
reader.onload = function(e) {
var res = e.target.result;
console.log(res);
};
var f = reader.readAsDataURL(file);
Anyone have any experience doing this locally?
Solutions like this (using XMLHttpRequest) get a cross-site
scripting error.
If using chrome or chromium browser, you could launch with --allow-file-access-from-files flag set to allow request of resource from local filesystem using XMLHttpRequest() or canvas.toDataURL().
You can use <img> element, <canvas> element .toDataURL() to create data URL of local image file without using XMLHttpRequest()
var file = "file.jpg";
var img = new Image;
var canvas = document.createElement("canvas");
var ctx = canvas.getContext("2d");
img.onload = function() {
canvas.width = this.naturalWidth;
canvas.height = this.naturalHeight;
ctx.drawImage(this, 0, 0);
var res = canvas.toDataURL("image/jpeg", 1); // set image `type` to `image/jpeg`
console.log(res);
}
img.src = file;
You could alternatively use XMLHttpRequest() as described at Convert local image to base64 string in Javascript.
See also How to print all the txt files inside a folder using java script .
For a details of difference of returned data URI from either approach see canvas2d toDataURL() different output on different browser
As described by #Kaiido at comment below
it will first decode it, at this stage it's still your file, then it
will paint it to the canvas (now it's just raw pixels) and finally it
will reencode it (it has nothing to do with your original file
anymore) check the dataURI strings... They're compeltely different and
even if you do the canvas operation from two different browsers,
you'll have different outputs, while FileReader will always give you
the same output, since it encode the file directly, it doesn't decode
it.

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