How can I parse a text file using javascript

How can I parse a text file using javascript - javascript

The code below is to read a text file using javascript. it works.
However, I just want to read part of the content.
For example, the content of the file is :"Hello world!"
I just want to display "Hello".
I tried function split(), but it only works on strings. I don't know how to insert it here.
var urls = ["data.txt"];
function loadUrl() {
var urlToLoad = urls[0];
alert("load URL ... " + urlToLoad);
browser.setAttributeNS(xlinkNS, "href", urlToLoad);
}
thank you!!!

I used
jQuery.get('http://localhost/foo.txt', function(data) {
var myvar = data;
});
, and got data from my text file.
Or try this
JQuery provides a method $.get which can capture the data from a URL. So to "read" the html/text document, it needs to be accessible through a URL. Once you fetch the HTML contents you should just be able to wrap that markup as a jQuery wrapped set and search it as normal.
Untested, but the general gist of it...
var HTML_FILE_URL = '/whatever/html/file.html';
$(document).ready(function() {
$.get(HTML_FILE_URL, function(data) {
var fileDom = $(data);
fileDom.find('h2').each(function() {
alert($(this).text());
});
});
});

Try this to read separate words if I understood correctly what you need.
Create a file with the contents "hello world" and browse to it with the example script.
The output is "hello".
<html>
<head>
<input type="file" id="fileinput" />
<script type="text/javascript">
function readSingleFile(evt) {
var f = evt.target.files[0];
if (f) {
var r = new FileReader();
r.onload = function(e) {
var contents = e.target.result;
var ct = r.result;
var words = ct.split(' ');
alert(words[0]);
}
r.readAsText(f);
} else {
alert("Failed to load file");
}
}
document.getElementById('fileinput').addEventListener('change', readSingleFile, false);
</script>
</head>
<body>
</body>
</html>
Reading directly has to be with an ajax request due to the javascript restrictions regarding safety.
This code shoudl perform the requested operation:
<html>
<head>
<input type="file" id="fileinput" />
<script type="text/javascript">
var xmlhttp = new XMLHttpRequest();
xmlhttp.onreadystatechange = function(){
if(xmlhttp.status==200 && xmlhttp.readyState==4){
var words = xmlhttp.responseText.split(' ');
alert(words[0]);
}
}
xmlhttp.open("GET","FileName.txt",true);
xmlhttp.send();
</script>
</head>
<body>
</body>
</html>

Opening a file in javascript with ajax (without using any framework)
var urls = ["data.txt"];
xhrDoc= new XMLHttpRequest();
xhrDoc.open('GET', urls[0] , async)
if (xhrDoc.overrideMimeType)
xhrDoc.overrideMimeType('text/plain; charset=x-user-defined')
xhrDoc.onreadystatechange =function()
{
if (this.readyState == 4)
{
if (this.status == 200)
{
var data= this.response; //Here is a string of the text data
}
}
}
xhrDoc.send() //sending the request

Related

Reading a OneDrive local JSON file using fetch in JavaScript [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.

HTML- How can I insert the contents of a .txt file into a variable to use .innerHTML to change the contents of <body>?

Im trying to create an automated system for HTML page handling where I will be able to change the contents
of a<div> inside <body> by writing into an external .txt file and uploading it to the server. Im still an early student in university
and I havent learned PHP and JQuery yet. So I am trying to accomplish this by using only Javascript and HTML.
I just need a way for whatever I write inside the .txt file to be written again inside the <div class="CONTENT" id="target"> which is inside the <body> automatically. Any thoughts and suggestions are greatly appreciated!

You can solve your problem by using the FileReader.
Have a look to
this answer.
function readSingleFile(e) {
var file = e.target.files[0];
if (!file) {
return;
}
var reader = new FileReader();
reader.onload = function (e) {
var contents = e.target.result;
displayContents(contents);
};
reader.readAsText(file);
}
function displayContents(contents) {
var element = document.getElementById('target');
element.textContent = contents;
}
document.getElementById('file-input')
.addEventListener('change', readSingleFile, false);
<html>
<head></head>
<body>
<input type="file" id="file-input" />
<h3>Contents of the file:</h3>
<div id="target" class="CONTENT"></div>
</body>
</html>

You can make an AJAX call for the text file and take the response from that call and set that as the .textContent of the div. Here's an example (see comments inline):
const output = document.getElementById("output");
// Create XHR object
var xhr = new XMLHttpRequest();
// Configure the request (substitute a URL
// to the file below)
xhr.open("GET", filePathHere, false);
// Set up the callback for when the response has
// been recieved
xhr.onreadystatechange = function (){
if(xhr.readyState === 4) {
// Was the request successful?
if(xhr.status === 200 || xhr.status == 0) {
// Populate the <div> with the response text
output.textContent = xhr.responseText;
}
}
}
xhr.send(null); // Make the call
<div id="output"></div>

I would like to load a list of urls to a var in any browsers' dev console (JavaScript)

I have a .txt file on my hard drive containing lots of URLs structured like this:
http://url1.com/
http://url2.com/
.
.
.
I want to load them to a var in Firefox's/Chrome's/IE's dev console so that it would be a vector of strings. I plan to visit these pages with a for loop. How can this be done?

<script>
var urls = [
'http://url1.com/',
'http://url2.com/'
];
</script>
You can generate this snippet with code or just have your file export a global variable and then load it via tags.

You can read a file via JavaScript from the page. You cannot upload a file to the developer's console.
I then modified the code bellow a bit to help you further. I added a scrape function that will help you request each URL one at a time.
<div id="page-wrapper">
<h1>Text File Reader</h1>
<div>
Select a text file:
<input type="file" id="fileInput">
</div>
<pre id="fileDisplayArea"><pre>
</div>
<script>
function scrape(urls) {
url = urls.shift()
$.get(function (url) {
// get the url data here
scrape(urls);
});
}
window.onload = function() {
var fileInput = document.getElementById('fileInput');
var fileDisplayArea = document.getElementById('fileDisplayArea');
fileInput.addEventListener('change', function(e) {
var file = fileInput.files[0];
var textType = /text.*/;
if (file.type.match(textType)) {
var reader = new FileReader();
reader.onload = function(e) {
scrape(reader.result.split("\n"));
}
reader.readAsText(file);
} else {
fileDisplayArea.innerText = "File not supported!"
}
});
}
</script>
Modified version of:
Read a local text file using Javascript

The only way di make your JavaScript aware of local files is to HTTP GET them.
So probably you have to put your file somewhere handy in the project folder and procees with an AJAX request.
var httpRequest;
function makeRequest() {
httpRequest = new XMLHttpRequest();
request.open("GET", "files/url.txt", false);
request.send(null);
saveArray(request.responseText);
}
var array = [];
saveArray(string){
array = string.split("\n")
}

You can get the contents of the file to show up in the Console with the below snippet.
var file="file://C:/FileName.txt";
function read(file)
{
var File = new XMLHttpRequest();
File.open("GET", file, false);
File.onreadystatechange = function ()
{
if(File.readyState === 4)
{
if(File.status === 200 || File.status == 0)
{
var Text = File.responseText;
console.log(Text);
}
}
}
File.send(null);
}

I found a simple but not very elegant workaround for the issue. I just copy and paste the list into a var definition. I don't have to do this often, so it is kind of okay.

How to read local text file into array list Javascript

I have a small html file that is supposed to display the contents of a text file onto the screen. The text (values.txt) is in the same file as the html file. It appears that when it reads the contents it doesn't get the values as they don't appear in the alert.
here is the code
<html>
<head>
<!--<input type="file" id="fileinput" />-->
<script type="text/javascript">
function readSingleFile(file) {
var f = new File([""], "filename.txt", {type: "text/plain"})
if (f) {
var r = new FileReader();
r.onload = function(e) {
var contents = e.target.result;
var ct = r.result;
var words = ct.split(' ');
alert(words[0] + 'test'); //this alert goes off but no values from words[0] are displayed
}
r.readAsText(f);
} else {
alert("Failed to load file");
}
}
//readSingleFile('values.txt');
</script>
</head>
<body onload="readSingleFile('values.txt')">
</body>
</html>
what can I do in order to read a text file into a list / get this code snippet to work?

The main problem is that first of all you need to get the file for your function. Just passing the file's name as argument is not enough.
Also is better to use an input of type file instead body with an onload attribute.
I've refactored your code in order to get it works.
1. Use this on your Html and delete body onload attribute.
<input id="inp" type="file" />">
Add this function to an external js file or wrap it between script tag inside your html file.
function readSingleFile(evt) {
var f = evt.target.files[0];
if (f) {
var r = new FileReader();
r.onload = function(e) {
var contents = e.target.result;
alert( "Got the file.n"
+"name: " + f.name + "n"
+"type: " + f.type + "n"
+"size: " + f.size + " bytesn"
+ "starts with: " + contents.substr(1, contents.indexOf("n"))
);
}
r.readAsText(f);
} else {
alert("Failed to load file");
}
}
// this parts gets the file and keeps an eye for changes
document.getElementById('inp').addEventListener('change', readSingleFile,false);
I hope you may find this useful.

Unfortunately I did'nt get it to work with your approach either. As Antonio682 suggested, it would be better to do it with an input-field, but you may aswell try it with an ajax-call :
<html>
<head>
<!--<input type="file" id="fileinput" />-->
<script type="text/javascript">
function readSingleFile(file) {
var objXMLhttp = new XMLHttpRequest()
objXMLhttp.open("GET", file, true);
objXMLhttp.send();
objXMLhttp.onreadystatechange = function(){
if (objXMLhttp.readyState == 4){
if(objXMLhttp.status == 200) {
var arrContents = objXMLhttp.responseText.split("\n");
console.log(arrContents);
} else {
console.log("error");
}
}
}
}
</script>
</head>
<body onload="readSingleFile('values.txt')">
</body>
</html>
You might want to test it with Firefox, since Chromes security settings dont allow file-protocol requests.
You can read more about ajax calls here

Is it possible to read the content of a file from JavaScript in the browser [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.

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