CSV File's Contents Null in Javascript - javascript

I am currently working on a website that will display a large amount of data from a csv I have already written. I want to first upload the data to javascript to manipulate the data before displaying it. The CSV file is in the root website directory.
Here is the code for what I have now:
var file = new File([""], "data.csv"
, {type:"text/plain", lastModified: new Date().getTime()});
const reader= new FileReader();
reader.onload = function() {
var contents = this.result
console.log(file)
console.log(contents)
},false;
reader.readAsText( file );
}
Right now, the file's contents are empty even though my CSV has 500 lines of data. How can I read in the CSV file into javascript so that the data can be manipulated and displayed. The CSV file will be the same every time and will be from the website directory and not from the user uploading a file.

I tried to get a file in localhost by using XHR and it worked.
Maybe you can try this.
My index.html and test.csv are in the same folder.
<script>
(() => {
var xhr = new XMLHttpRequest();
xhr.open("GET", "test.csv", true);
xhr.onreadystatechange = function()
{
if (this.readyState == 4 && this.status == 200) {
console.log(xhr.responseText);
}
};
xhr.send();
})();
</script>

Related

How do I read a local file in JavaScript using relative addressing

I am writing a widget (discord) to upload to a website (so I can't use absolute as the location of the config file will change when I upload it) and I made a configuration file under the same directory. Is there a way to access this config file so my widget can read it wherever it is placed.
JavaScript Code:
function readTextFile(file, callback) {
var rawFile = new XMLHttpRequest();
rawFile.overrideMimeType("application/json");
rawFile.open("GET", file, true);
rawFile.onreadystatechange = function() {
if (rawFile.readyState === 4 && rawFile.status == "200") {
callback(rawFile.responseText);
}
}
rawFile.send(null);
}
var json_url;
readTextFile("config.json", function(text){ //read the configuration file (config.json)
var config = JSON.parse(text);
json_url = "https://discordapp.com/api/guilds/" + config.server_id + "/widget.json";
console.log(config.server_id); //debug line
});
JSON:
{
"server_id" : "XXXXXXXXXXXXXXXXXX",
"invite_link" : "https://discord.gg/XXXXXXX"
}

Read a specific local file [duplicate]

I’m trying to implemennt a simple text file reader by creating a function that takes in the file’s path and converts each line of text into a char array, but it’s not working.
function readTextFile() {
var rawFile = new XMLHttpRequest();
rawFile.open("GET", "testing.txt", true);
rawFile.onreadystatechange = function() {
if (rawFile.readyState === 4) {
var allText = rawFile.responseText;
document.getElementById("textSection").innerHTML = allText;
}
}
rawFile.send();
}
What is going wrong here?
This still doesn’t seem to work after changing the code a little bit from a previous revision and now it's giving me an XMLHttpRequest exception 101.
I’ve tested this on Firefox and it works, but in Google Chrome it just won't work and it keeps giving me an Exception 101. How can I get this to work on not just Firefox, but also on other browsers (especially Chrome)?
You need to check for status 0 (as when loading files locally with XMLHttpRequest, you don't get a status returned because it's not from a Webserver)
function readTextFile(file)
{
var rawFile = new XMLHttpRequest();
rawFile.open("GET", file, false);
rawFile.onreadystatechange = function ()
{
if(rawFile.readyState === 4)
{
if(rawFile.status === 200 || rawFile.status == 0)
{
var allText = rawFile.responseText;
alert(allText);
}
}
}
rawFile.send(null);
}
And specify file:// in your filename:
readTextFile("file:///C:/your/path/to/file.txt");
After the introduction of fetch api in javascript, reading file contents could not be simpler.
reading a text file
fetch('file.txt')
.then(response => response.text())
.then(text => console.log(text))
// outputs the content of the text file
reading a json file
fetch('file.json')
.then(response => response.json())
.then(jsonResponse => console.log(jsonResponse))
// outputs a javascript object from the parsed json
Update 30/07/2018 (disclaimer):
This technique works fine in Firefox, but it seems like Chrome's fetch implementation does not support file:/// URL scheme at the date of writing this update (tested in Chrome 68).
Update-2 (disclaimer):
This technique does not work with Firefox above version 68 (Jul 9, 2019) for the same (security) reason as Chrome: CORS request not HTTP. See https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS/Errors/CORSRequestNotHttp.
Visit Javascripture ! And go the section readAsText and try the example. You will be able to know how the readAsText function of FileReader works.
var openFile = function(event) {
var input = event.target;
var reader = new FileReader();
reader.onload = function() {
var text = reader.result;
var node = document.getElementById('output');
node.innerText = text;
console.log(reader.result.substring(0, 200));
};
reader.readAsText(input.files[0]);
};
<input type='file' accept='text/plain' onchange='openFile(event)'><br>
<div id='output'>
...
</div>
var input = document.getElementById("myFile");
var output = document.getElementById("output");
input.addEventListener("change", function () {
if (this.files && this.files[0]) {
var myFile = this.files[0];
var reader = new FileReader();
reader.addEventListener('load', function (e) {
output.textContent = e.target.result;
});
reader.readAsBinaryString(myFile);
}
});
<input type="file" id="myFile">
<hr>
<textarea style="width:500px;height: 400px" id="output"></textarea>
Modern solution:
Use fileOrBlob.text() as follows:
<input type="file" onchange="this.files[0].text().then(t => console.log(t))">
When user uploads a text file via that input, it will be logged to the console. Here's a working jsbin demo.
Here's a more verbose version:
<input type="file" onchange="loadFile(this.files[0])">
<script>
async function loadFile(file) {
let text = await file.text();
console.log(text);
}
</script>
Currently (January 2020) this only works in Chrome and Firefox, check here for compatibility if you're reading this in the future: https://developer.mozilla.org/en-US/docs/Web/API/Blob/text
On older browsers, this should work:
<input type="file" onchange="loadFile(this.files[0])">
<script>
async function loadFile(file) {
let text = await (new Response(file)).text();
console.log(text);
}
</script>
Related: As of September 2020 the new Native File System API available in Chrome and Edge in case you want permanent read-access (and even write access) to the user-selected file.
Yes JS can read local files (see FileReader()) but not automatically: the user has to pass the file or a list of files to the script with an html <input type="file">.
Then with JS it is possible to process (example view) the file or the list of files, some of their properties and the file or files content.
What JS cannot do for security reasons is to access automatically (without the user input) to the filesystem of his computer.
To allow JS to access to the local fs automatically is needed to create not an html file with JS inside it but an hta document.
An hta file can contain JS or VBS inside it.
But the hta executable will work on windows systems only.
This is standard browser behavior.
Also Google Chrome worked at the fs API, more info here: http://www.html5rocks.com/en/tutorials/file/filesystem/
Using Fetch and async function
const logFileText = async file => {
const response = await fetch(file)
const text = await response.text()
console.log(text)
}
logFileText('file.txt')
Try creating two functions:
function getData(){ //this will read file and send information to other function
var xmlhttp;
if (window.XMLHttpRequest) {
xmlhttp = new XMLHttpRequest();
}
else {
xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange = function () {
if (xmlhttp.readyState == 4) {
var lines = xmlhttp.responseText; //*here we get all lines from text file*
intoArray(lines); *//here we call function with parameter "lines*"
}
}
xmlhttp.open("GET", "motsim1.txt", true);
xmlhttp.send();
}
function intoArray (lines) {
// splitting all text data into array "\n" is splitting data from each new line
//and saving each new line as each element*
var lineArr = lines.split('\n');
//just to check if it works output lineArr[index] as below
document.write(lineArr[2]);
document.write(lineArr[3]);
}
Provably you already try it, type "false" as follows:
rawFile.open("GET", file, false);
other example - my reader with FileReader class
<html>
<head>
<link rel="stylesheet" href="http://code.jquery.com/ui/1.11.3/themes/smoothness/jquery-ui.css">
<script src="http://code.jquery.com/jquery-1.10.2.js"></script>
<script src="http://code.jquery.com/ui/1.11.3/jquery-ui.js"></script>
</head>
<body>
<script>
function PreviewText() {
var oFReader = new FileReader();
oFReader.readAsDataURL(document.getElementById("uploadText").files[0]);
oFReader.onload = function (oFREvent) {
document.getElementById("uploadTextValue").value = oFREvent.target.result;
document.getElementById("obj").data = oFREvent.target.result;
};
};
jQuery(document).ready(function(){
$('#viewSource').click(function ()
{
var text = $('#uploadTextValue').val();
alert(text);
//here ajax
});
});
</script>
<object width="100%" height="400" data="" id="obj"></object>
<div>
<input type="hidden" id="uploadTextValue" name="uploadTextValue" value="" />
<input id="uploadText" style="width:120px" type="file" size="10" onchange="PreviewText();" />
</div>
Source file
</body>
</html>
This might help,
var xmlhttp = window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject("Microsoft.XMLHTTP");
xmlhttp.onreadystatechange = function () {
if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
alert(xmlhttp.responseText);
}
}
xmlhttp.open("GET", "sample.txt", true);
xmlhttp.send();
Local AJAX calls in Chrome are not supported due to same-origin-policy.
Error message on chrome is like this:
"Cross origin requests are not supported for protocol schemes: http, data, chrome, chrome-extension, https."
This means that chrome creates a virtual disk for every domain to keep the files served by the domain using http/https protocols. Any access to files outside this virtual disk are restricted under same origin policy. AJAX requests and responses happen on http/https, therefore wont work for local files.
Firefox does not put such restriction, therefore your code will work happily on the Firefox. However there are workarounds for chrome too : see here.
Adding to some the above answers, this modified solution worked for me.
<input id="file-upload-input" type="file" class="form-control" accept="*" />
....
let fileInput = document.getElementById('file-upload-input');
let files = fileInput.files;
//Use createObjectURL, this should address any CORS issues.
let filePath = URL.createObjectURL(files[0]);
....
function readTextFile(filePath){
var rawFile = new XMLHttpRequest();
rawFile.open("GET", filePath , true);
rawFile.send(null);
rawFile.onreadystatechange = function (){
if(rawFile.readyState === 4){
if(rawFile.status === 200 || rawFile.status == 0){
var allText = rawFile.responseText;
console.log(allText);
}
}
}
}
function readTextFile(file) {
var rawFile = new XMLHttpRequest(); // XMLHttpRequest (often abbreviated as XHR) is a browser object accessible in JavaScript that provides data in XML, JSON, but also HTML format, or even a simple text using HTTP requests.
rawFile.open("GET", file, false); // open with method GET the file with the link file , false (synchronous)
rawFile.onreadystatechange = function ()
{
if(rawFile.readyState === 4) // readyState = 4: request finished and response is ready
{
if(rawFile.status === 200) // status 200: "OK"
{
var allText = rawFile.responseText; // Returns the response data as a string
console.log(allText); // display text on the console
}
}
}
rawFile.send(null); //Sends the request to the server Used for GET requests with param null
}
readTextFile("text.txt"); //<= Call function ===== don't need "file:///..." just the path
- read file text from javascript
- Console log text from file using javascript - Google chrome and mozilla firefox in my case i have this structure of files :
the console.log result :
How to read a local file?
By using this you will load a file by loadText() then JS will asynchronously wait until the file is read and loaded after that it will execture readText() function allowing you to continue with your normal JS logic (you can also write a try catch block on the loadText() function in the case any error arises) but for this example I keep it at minimal.
async function loadText(url) {
text = await fetch(url);
//awaits for text.text() prop
//and then sends it to readText()
readText(await text.text());
}
function readText(text){
//here you can continue with your JS normal logic
console.log(text);
}
loadText('test.txt');
If you want to prompt the user to select a file, then read its contents:
// read the contents of a file input
const readInputFile = (inputElement, callback) => {
const reader = new FileReader();
reader.onload = () => {
callback(reader.result)
};
reader.readAsText(inputElement.files[0]);
};
// create a file input and destroy it after reading it
const openFile = (callback) => {
var el = document.createElement('input');
el.setAttribute('type', 'file');
el.style.display = 'none';
document.body.appendChild(el);
el.onchange = () => {readInputFile(el, (data) => {
callback(data)
document.body.removeChild(el);
})}
el.click();
}
Usage:
// prompt the user to select a file and read it
openFile(data => {
console.log(data)
})
<html>
<head>
<title></title>
<meta charset="utf-8" />
<script src="https://code.jquery.com/jquery-1.10.2.js"></script>
<script type="text/javascript">
$(document).ready(function () {
$.ajax({`enter code here`
url: "TextFile.txt",
dataType: "text",
success: function (data) {
var text = $('#newCheckText').val();
var str = data;
var str_array = str.split('\n');
for (var i = 0; i < str_array.length; i++) {
// Trim the excess whitespace.
str_array[i] = str_array[i].replace(/^\s*/, "").replace(/\s*$/, "");
// Add additional code here, such as:
alert(str_array[i]);
$('#checkboxes').append('<input type="checkbox" class="checkBoxClass" /> ' + str_array[i] + '<br />');
}
}
});
$("#ckbCheckAll").click(function () {
$(".checkBoxClass").prop('checked', $(this).prop('checked'));
});
});
</script>
</head>
<body>
<div id="checkboxes">
<input type="checkbox" id="ckbCheckAll" class="checkBoxClass"/> Select All<br />
</div>
</body>
</html>
Get local file data in js(data.js) load:
function loadMyFile(){
console.log("ut:"+unixTimeSec());
loadScript("data.js?"+unixTimeSec(), loadParse);
}
function loadParse(){
var mA_=mSdata.split("\n");
console.log(mA_.length);
}
function loadScript(url, callback){
var script = document.createElement("script")
script.type = "text/javascript";
if (script.readyState){ //IE
script.onreadystatechange = function(){
if (script.readyState == "loaded" ||
script.readyState == "complete"){
script.onreadystatechange = null;
callback();
}
};
} else { //Others
script.onload = function(){
callback();
};
}
script.src = url;
document.getElementsByTagName("head")[0].appendChild(script);
}
function hereDoc(f) {
return f.toString().
replace(/^[^\/]+\/\*![^\r\n]*[\r\n]*/, "").
replace(/[\r\n][^\r\n]*\*\/[^\/]+$/, "");
}
function unixTimeSec(){
return Math.round( (new Date()).getTime()/1000);
}
file of data.js like:
var mSdata = hereDoc(function() {/*!
17,399
1237,399
BLAHBLAH
BLAHBLAH
155,82
194,376
*/});
dynamic unixTime queryString prevents cached.
AJ works in web http://.
This function made for browsers and open file picker dialog and after user selection read file as binary and call callback function with read data:
function pickAndReadFile(callback) {
var el = document.createElement('input');
el.setAttribute('type', 'file');
el.style.display = 'none';
document.body.appendChild(el);
el.onchange = function (){
const reader = new FileReader();
reader.onload = function () {
callback(reader.result);
document.body.removeChild(el);
};
reader.readAsBinaryString(el.files[0]);
}
el.click();
}
And use it like this:
pickAndReadFile(data => {
console.log(data)
})
This is an old question but there two main ideas that we have to be clear. Do we want to read the whole file or get it line by line?
Teo, I want to get the whole file and process it later.
Okay that is very easy we just call text (remember that text assumes that the file is encoded as UTF-8) and handle the file like this:
const $output = document.getElementById('output')
const $file = document.getElementById('file')
const fetchFile = async e => {
const [file] = e.target.files
const text = await file.text()
$output.textContent = text
}
$file.onchange = fetchFile
<input id='file' type='file' accept='text/plain'><br>
<pre id='output'>...</pre>
What about line by line? It is possible?.
Well my young Padawan, that is also possible we just need a split the text in lines like this
const $output = document.getElementById('output')
const $file = document.getElementById('file')
let count
const fetchFile = async e => {
const [file] = e.target.files
if (!file) return
count = 0
const text = await file.text()
$output.textContent = text
const lines = text.split(/\r?\n/gm)
for (const line of lines) {
if (line) count++
}
console.log({count})
}
$file.onchange = fetchFile
<input id='file' type='file' accept='text/plain'><br>
<pre id='output'>...</pre>
You can import my library:
<script src="https://www.editeyusercontent.com/preview/1c_hhRGD3bhwOtWwfBD8QofW9rD3T1kbe/code.js?pe=yikuansun2015#gmail.com"></script>
then, the function fetchfile(path) will return the uploaded file
<script src="https://www.editeyusercontent.com/preview/1c_hhRGD3bhwOtWwfBD8QofW9rD3T1kbe/code.js"></script>
<script>console.log(fetchfile("file.txt"))</script>
Please note: on Google Chrome if the HTML code is local, errors will appear, but saving the HTML code and the files online then running the online HTML file works.
In order to read a local file text through JavaScript using chrome, the chrome browser should run with the argument --allow-file-access-from-files to allow JavaScript to access local file, then you can read it using XmlHttpRequest like the following:
var xmlhttp = new XMLHttpRequest();
xmlhttp.onreadystatechange = function () {
if (xmlhttp.readyState == 4) {
var allText = xmlhttp.responseText;
}
};
xmlhttp.open("GET", file, false);
xmlhttp.send(null);
I know, I am late at this party. Let me show you what I have got.
This is a simple reading of text file
var path = "C:\\path\\filename.txt"
var fs = require('fs')
fs.readFile(path , 'utf8', function(err, data) {
if (err) throw err;
console.log('OK: ' + filename);
console.log(data)
});
I hope this helps.

Edit and Send back Image File User Uploads

I'm building a front-end interface for a back-end image edited process (don't know all the correct jargon).
Basically:
user should be able to upload an image file through the UI
which sends it to the server
where the image is edited in some way
then the UI should display the edited image
I'm using an XHR request with the POST method as shown below to send the image file to the server.
var fileSelect = document.getElementById('file-select');
var uploadButton = document.getElementById('upload-button');
uploadButton.onclick = function() {
this.innerHTML = 'Uploading...';
//---------------
var files = fileSelect.files
var formData = new FormData();
var file = files[0]
if (file.type.match('image.*')) {
formData.append('photos[]', file, file.name);
}
var xhr = new XMLHttpRequest();
xhr.open('POST', 'http://httpbin.org/post', true);
xhr.onload = function() {
if (xhr.status === 200) {
uploadButton.innerHTML = 'Upload';
}
else {
alert('An error occurred!');
}
};
xhr.send(formData);
}; //end on-click 'Upload'
<input type="file" id="file-select" name="photos[]"/>
<button type="submit" id="upload-button">Upload</button>
My question is: In general, once the image file is sent to the server, by the code above, when/how does the edited image get sent back?
Will it be sent back as part of the server response to my POST request, and thus accessible in my processRequest callback function (assuming the server is configured to process it that way)?
Do I have to send a GET request to get the edited file?
I do not have access to the server/back-end at this point in time, and just know how the UI is supposed to work.

Image src not updating after setRequestHeader call

I have two AJAX functions: one for an image file upload, one for a form info upload.
File Upload
function uploadFile(insertNodeID, inputFileID){
var img = document.getElementById(inputFileID).files[0];
var form_data = new FormData();
form_data.append('file[]', img, img.name);
var objXML = new XMLHttpRequest();
objXML.onprogress = updateProgress;
objXML.onload = function() {
if(objXML.readyState==4 && objXML.status==200) {
if(objXML.responseText !== 'no'){
document.getElementById(insertNodeID).src = objXML.responseText;
}
else{
errorInOut('There was a problem uploading the file.');
}
}
};
objXML.open('POST', baseURL+'ajax/admin_fileupload/', true);
objXML.send(form_data);
Form Info Upload
function uploadFormInfo(strURL, strData, type) {
strURL = baseURL+'ajax/'+strURL+'/';
var objXML = new XMLHttpRequest();
objXML.onreadystatechange = function() {
if (objXML.readyState == 4 && objXML.status == 200) {
returnXML(objXML.responseText, type);
}
};
objXML.open("POST", strURL, true);
objXML.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
objXML.send(strData);
They both work perfect independently.
The issue I'm running into is when I call the uploadFormInfo(), then call uploadFile(), the document.getElementById(insertNodeID).src does not render the uploaded image. It still uploads the image to the server and the responseText is the correct path to the image. I did a console.log on the .src of the id AFTER the I plugged in the new image and the .src is correct BUT, it never changes in the elements tab in Chome inspect. It also works fine BEFORE I call uploadFormInfo().
I've tried and number of things (sending a separate request header for the uploadFile) and nothing works.
I'm stumped.

Upload file from HTML5 Filesystem by XMLHttpRequest

Trying to Upload some Images stored in Filesystem of Google Chrome.
But Im not able to upload the Image. Any Idea how to do it?
The Server receives an empty array. The Code of posttest.php is just print_r($_POST)
var xhr = new XMLHttpRequest();
xhr.open('POST', '/posttest.php', true);
xhr.onload = function(e) {
if (this.status == 200) {
console.log(this.responseText);
}
};
window.resolveLocalFileSystemURL(image, function(fileEntry) {
fileEntry.file(function(file) {
var reader = new FileReader();
reader.onloadend = function(e) {
var formData = new FormData();
formData.append('image', this.result);
xhr.send(formData);
};
reader.readAsText(file);
});
});
this is the Javascript function that worked for me in chrome
function upload(filename) {
var xhr = new XMLHttpRequest();
xhr.open("post", "upload.php", true);
window.resolveLocalFileSystemURL = window.resolveLocalFileSystemURL || window.webkitResolveLocalFileSystemURL;
filename = 'filesystem:http://localhost/temporary/' + filename;
window.resolveLocalFileSystemURL(filename, function(fileEntry) {
fileEntry.file(function(file) {
xhr.setRequestHeader("Content-Type", "multipart/form-data");
xhr.setRequestHeader("X-File-Name", file.name);
xhr.setRequestHeader("X-File-Size", file.size);
xhr.setRequestHeader("X-File-Type", file.type);
xhr.send(file);
});
});
}
Now most people on the skip the upload.php taking it for granted. But it is very important and so I paste it here:
<?php
// I had to figure out what is getting passed using var_dump($_SERVER)
$fn = (isset($_SERVER['HTTP_X_FILE_NAME']) ? $_SERVER['HTTP_X_FILE_NAME'] : false);
if ($fn) {
// AJAX call
file_put_contents(
'uploads/' . $fn,
file_get_contents('php://input')
);
echo "$fn uploaded";
exit();
}
?>
Hope this helps someone, I wasted an entire day to figure this out !
First of all, your comment isn't exactly correct, the PHP code shouldn't even be receiving a blob. It's just receiving text, because you read the file as text, while png images (and almost all image types) aren't supposed to be text, they're supposed to be binary. And Blobs themselves are perfect for storing binary data, so you don't even need to use a FileReader, you can just send the Blob itself through XMLHttpRequest!
Here is how the revised fileEntry.file callback function should look:
fileEntry.file(function(file) {
xhr.send(file);
});
It's that simple! No need to read the Blob. However, you need to do some more stuff on the
PHP side now. This code will write the contents of the uploaded image to disk, then create an <img> element that allows you to view it. Here's how the PHP /posttest.php should look for that:
<?php
$rhand=fopen('php://input','r');
$cont=fread($rhand,filesize('php://input'));
fclose($rhand);
$whand=fopen('./uploaded.png','w');
fwrite($whand,$cont);
fclose($whand);
?>
<img src="uploaded.png">
It should be pretty clear what that does if you know that php://input is where php will get input from a post request if it doesn't have a MIME type that allows it to easily put it into $_POST (For example, when you have have a request with MIME type application/x-www-form-urlencoded, PHP recognizes it and is able to parse the POST contents into $_POST, but with a Blob, it doesn't, so it just outputs it out of php://input)
Please note that none of this is tested, please put a comment if it doesn't work and I'll try to fix it!
Having encountered the same challenge myself, I was able to come up with a very sleek solution. The key is to create a new Blob, from the file object returned by the fileEntry.
window.resolveLocalFileSystemURL = window.resolveLocalFileSystemURL || window.webkitResolveLocalFileSystemURL;
window.resolveLocalFileSystemURL(image, function (fileEntry) {
fileEntry.file(function (file) {
var formData = new FormData();
var tempBlob=new Blob([this.result], {type:this.result.type});
formData.append('image', tempBlob);
});
});

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