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Uploading files using js fileReader results in corrupted files

I am trying to upload a file using js file reader and AJAX to my server.
I used FileAPI and fileReader to read the file and convert it to string and then send it to the server via an AJAX request.
Here is my client side js code :
function upload() {
var file = document.getElementById('periodExcel').files[0];
if (file) {
console.log(file);
var reader = new FileReader();
reader.readAsText(file, file.type);
console.log(reader);
reader.onload = uploadAndRun;
}
}
function uploadAndRun(event) {
console.log(event);
var result = event.target.result;
$('#js').html(result);
var fileName = document.getElementById('periodExcel').files[0].name; //Should be 'picture.jpg'
$.post('./upload.php', {data: result, name: fileName}, function(result2){
$('#php').html(result2);
});
}
Here is the upload php script:
file_put_contents('upload/' . $_POST['name'], $_POST['data']);
it just write the file using php file_put_contents function.
My problem is that the uploaded file is corrupted and has a different size than the original file (it is larger).
I tried to use php file_get_contents function to read the same file and write it again using file_put_contents and the result file was fine and same as the original one.
I then tried to compare the two strings (the one that comes from the file reader and the one that comes from file_get_contents ) and compares the two strings using strcmp, that gives me that the string that come from the fileReader is larger than the one comes from file_get_contents.
So, what is the problem with my code and how to use the FileReader to upload file in this way while using readAsText function.

You are using the wrong collection in PHP. To access uploaded file stream use $_FILES.
See here:
http://php.net/manual/en/reserved.variables.files.php
and here: http://php.net/manual/en/features.file-upload.post-method.php
In short, PHP runtime takes care of reading the upload stream from the HTTP request, stores it locally in a temp folder and exposes the above map for you to access the temp file and possibly move it to another location (or do whatever else you need to do with it).

Load a 'server-side' file with XMLHttpRequest in local html file

I want to load a json-stringified file in my javascript. The javascript reside in a html-file which I load from my local file system.
I have tried with the following code:
var xhr = new XMLHttpRequest();
xhr.open('GET', fileName, true);
xhr.responseType = 'blob';
xhr.onload = function(e) {
if (this.status == 200) {
// get binary data as a response
var blob = this.response;
alert("Yo");
}
};
But the onload event fires only once, with the status=0, then no more happens.
I have tried to use both a full path to the file as well as a local file path like "/files/the_file.txt".
It looks like the problem is related with me trying to run the html file locally. I don't want to set-up a local server as I have seen proposed in similar posts here at so.
Anyone out there with a solution to this problem?
EDIT:
This is not what I want, but this might serve to give an example of how I almost want it. This example let the user select a file, and my script can now access the content of the selected file.
HTML:
<input type="file" id="FancyInputField" onchange="doIt();">
Javascript:
function doIt(){
var selectedFile = document.getElementById('FancyInputField').files[0];
reader = new FileReader();
reader.onload = function (e) {
var output = reader.result;
var daObject = JSON.parse(output);
}
reader.readAsText(selectedFile);
}
This also works with a local html file. (No local server)
My question stands; How do I read the file(s) with no user interaction? The files reside in a sub-folder to where the html file are located. I can with no problem load and show an image from the same sub-folder, with an <img> tag. ..So why is it so difficult to load a text file?

How do I read the file(s) with no user interaction?
You can't. Those files belong to the user, not your website. You can't choose to read them.
I can with no problem load and show an image from the same sub-folder, with an <img> tag
There is a lot of difference between displaying an image to the user, and making the content of a file available to JavaScript code written by the page author.
So why is it so difficult to load a text file?
Send someone an HTML document in an email
Enjoy the JavaScript in it scooping up files from the hard disk and sending them to Joe Evil Hacker's server
It's just basic security.

Use URL.createObjectURL(file), instead of ajax.

Extracting excel content from client side Web Application

I have a web application (ASP.Net) that needs to upload a file
I've been looking for a framework to extract data from excel on the client side and submit the content (JSON, CSV) format into the server side to lessen the traffic. I've looked into ActiveXObject in javascript but it only works in internet explorer. I have an option to use silverlight or actionscript to do the parsing.
Question:
Is silverlight really dead? can't i use it on the long run?
Is this possible using action script?
Is there any javascript framework to do this kind of parsing?
Thanks in advance

You can use JS-XLSX JavaScript library to parse file on client side and then send the content of parsed spreadsheet to the server.
For example you can create a button (see HTML code below), then call loadBinaryFile() on change event, parse it with JS-XLSX library and send it to the server with $.post() or other similar function.
The structure of workbook is a JSON object and it is well described in documentation at JS-XLSX site.
<script src="http://alasql.org/console/xlsx.core.min.js"></script>
<input type="file" onchange="parseAndSend(event)" value="Parse and send XSLS file">
<script>
function parseAndSend (event) {
// Load binary file from desktop
loadBinaryFile(event,function(data){
// Parse it to JSON
var workbook = XLSX.read(data,{type:'binary'});
// Send to server data from workbook here
// $.post({url:'http://mypostaddress',data:workbook});
alert(workbook.SheetNames);
});
}
function loadBinaryFile(path, success) {
var files = path.target.files;
var reader = new FileReader();
var name = files[0].name;
reader.onload = function(e) {
var data = e.target.result;
success(data);
};
reader.readAsBinaryString(files[0]);
}
</script>

JPEG data obtained from FileReader doesn't match data in file

I'm trying to select a local JPEG file in the web browser via the HTML5 FileReader so I can submit it to a server without reloading the page. All the mechanics are working and I think I'm transferring and saving the exact data that JavaScript gave me, but the result is an invalid JPEG file on the server. Here's the basic code that demonstrates the problem:
<form name="add_photos">
​<input type=​"file" name=​"photo" id=​"photo" /><br />
​<input type=​"button" value=​"Upload" onclick=​"upload_photo()​;​" />​
</form>
<script type="text/javascript">
function upload_photo() {
file = document.add_photos.photo.files[0];
if (file) {
fileReader = new FileReader();
fileReader.onload = upload_photo_ready;
fileReader.readAsBinaryString(file);
}
}
function upload_photo_ready(event) {
data = event.target.result;
// alert(data);
URL = "submit.php";
ajax = new XMLHttpRequest();
ajax.open("POST", URL, 1);
ajax.setRequestHeader("Ajax-Request", "1");
ajax.send(data);
}
</script>
Then my PHP script does this:
$data = file_get_contents("php://input");
$filename = "test.jpg";
file_put_contents($filename, $data);
$result = imagecreatefromjpeg($filename);
That last line throws a PHP error "test.jpg is not a valid JPEG file." If I download the data back to my Mac and try to open it in Preview, Preview says the file "may be damaged or use a file format that Preview doesn’t recognize."
If I open both the original file on my desktop and the uploaded file on the server in text editors to inspect their contents, they are almost but not quite the same. The original file starts like this:
ˇÿˇ‡JFIFˇ˛;CREATOR: gd-jpeg v1.0 (using IJG JPEG v62), quality = 90
But the uploaded file starts like this:
ÿØÿàJFIFÿþ;CREATOR: gd-jpeg v1.0 (using IJG JPEG v62), quality = 90
Interestingly, if I view the data in a JavaScript alert with the commented-out line above, it looks just like the uploaded file's data, so it seems as if the FileReader isn't giving the correct data at the very beginning, as opposed to a problem that is introduced while transferring or saving the data on the server. Can anyone explain this?
I'm using Safari 6 and I also tried Firefox 14.
UPDATE: I just figured out that if I skip the FileReader code and change ajax.send(data) to ajax.send(file), the image is transferred and saved correctly on the server. So my problem is basically solved, but I'll award the answer points to anyone who can explain why my original approach with readAsBinaryString didn't work.

Your problem lies with readAsBinaryString. This will transfer the binary data byte-for-byte into a string, so that you will send a text string to your PHP file. Now a text string always has an encoding; and when you use XmlHttpRequest to upload a string, by default it will use UTF-8.
So each character, which was originally supposed to represent one byte, will be encoded as UTF-8... which uses multiple bytes for each character with a code point above 127!
Your best best is to use readAsArrayBuffer instead of readAsBinaryString. This will avoid all the character set conversions (that are necessary when dealing with strings).

Creating download prompt using purely javascript

I have some text data (say var a = 'Hello World From Javascript';)in javascript variable in current window. I want to do the following
through javascript-
1. open a new window and write the text data to the window.
2. set the content type to text/plain.
3. set the content-disposition to attachment, so that download prompt comes.
4. user downloads the text data as a text file and saves it to his local disk.
is this all possible through javascript?
I know we can make ajax calls to server or redirect but in this case instead of following above steps. But in this case, these workarounds are not adaptable.

you can do that using JS & HTML5 features. Please find below a sample code.
var fileParts = ['Hello World From Javascript'];
// Create a blob object.
var bb = new Blob(fileParts,{type : 'text/plain'});
// Create a blob url for this.
var dnlnk = window.URL.createObjectURL(bb);
var currentLnk = $('#blobFl').attr('href');
// blobFl is the id of the anchor tag through which the download will be triggered.
$('#blobFl').attr('href',dnlnk);
$('#blobFl').attr('download','helloworld.txt');
// For some reason trigger from jquery dint work for me.
document.getElementById('blobFl').click();

Triggering a file download without any server request
Unfortunately this is not something you can do with normal browser capabilities. Something like flash or a browser-specific plugin will get you what you need, but security limitations within javascript will not let you download arbitrary data created within the browser.
Also the 'data' url is not supported across all browser/version combinations. I am not sure if your users are constrained on what browser they are using or not but that may limit what you can do with that solution.
Source: Triggering a file download without any server request

If you already have the file on the server (I make an ajax call to generate and save a PDF on the server) - you can do this
window.location.replace(fileUrl);

No, Content-Disposition is a response header, it has to come from the server. I think you could do it with Flash but I wouldn't recommend it.

Here's a clean, pure js version of #Rajagopalan Srinivasan's answer:
var fileParts = ["Hello World From Javascript"];
// The anchor tag to use.
const blobLink = document.getElementById("blobLink");
// Create a blob object.
var blob = new Blob(fileParts, { type: "text/plain" });
// Create a blob url for this.
var blobUrl = window.URL.createObjectURL(blob);
blobLink.setAttribute("href", blobUrl);
blobLink.setAttribute("download", "helloworld.txt");
blobLink.click();
<a id="blobLink">Download</a>