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Get text from a link in javascript

I am trying to get text from a service on the same server as my webserver. The link is something like this:
http://<OwnIPadres>:8080/calc/something?var=that
This is my code:
function httpGet(theUrl)
{
alert(theUrl);
var doc = new XMLHttpRequest();
doc.onreadystatechange = function() {
if (doc.readyState == XMLHttpRequest.DONE) {
alert("text: " + doc.responseText );
document.getElementById('ctm').text = doc.responseText;
}
}
doc.open("get", theUrl);
doc.setRequestHeader("Content-Encoding", "UTF-8");
doc.send();
}
The url that i print in my first alert is the good one if i test in my browser, it is an html page with a table in it. But the alert of my text is empty? Is it a problem that the text is html?

Actually, its quite ok that your 'text' is 'html'. The problem is that using a different port counts as cross-site scripting. Therefore, your XMLHttpRequest is being stopped by the browser before it actually reaches your page across port 8080.
I'm not sure what else you're doing before and around this code snippet, but you could try an iframe call to your url to get your data, or you could add an
Access-Control-Allow-Origin: http://:8080/
in your header (however that will only get you the most modern browsers).
Finally, you could pull in a JS framework like JQuery which could help you with pulling in this service data.

XML, Javascript - Cannot call method getElementsByTagName of null

I am working on a little website idea, and I am not very great at any of this. I basically have an HTML quiz that will prompt the user with questions that I defined in an XML.
window.onload = function xml()
{
// get form from HTML
var form = document.getElementById("form");
// get XML document
if (window.XMLHttpRequest)
{
var xmlhttp = new XMLHttpRequest();
}
// open XML
xmlhttp.open("GET", "questions.xml", false);
xmlhttp.send(null);
// initialize elements for do document, questions, and details
var xmlDoc = xmlhttp.responseXML;
var question = xmlDoc.getElementsByTagName("question");
On the line above, I get an error saying "Cannot call method 'getElementsByTagName' of null". The strange thing, however, is that I only get said error if the XML file has multiple "question" tags. If I only have one "question" tag in my XML, the whole function works perfectly. So I am wondering what is going on in this case, and why it won't work for me.
(the rest of the code below shows where I begin to go with the function)
var qXML = xmlDoc.getElementsByTagName("q");
// write values into HTML for each question
for ( i = 0 ; i < question.length ; i++ )
{
// qBlock div for question
var div = document.createElement('div');
div.className = "qBlock";
This code continues for a while to get all fields in the HTML. In total, this block of code in the loop works all the way throughout, unless there are multiple "question" elements.
Thank you so much to anyone who can help / teach me on any of this. Also feel free to tell me if I am doing anything else incorrectly. I am open to any criticism.

While I can't be sure this is the problem without seeing your questions.xml file, you may have multiple root elements. For example:
<?xml version="1.0"?>
<question>...</question>
<question>...</question>
XML does not allow that, and it will fail to parse. Wrap them up in one root element:
<?xml version="1.0"?>
<questions>
<question>...</question>
<question>...</question>
</questions>

Having an error reading a text file with javascript

I've been trying to learn how to read a text file locally using JavaScript and Ajax. I've been looking on some tutorials online, and have followed them, but no matter what I do I cannot get my text to display what is in the .txt file.
function loadDoc(){
var xmlhttp = new XMLHttpRequest();
xmlhttp.onreadystatechange=function(){
if (xmlhttp.readyState==4 && xmlhttp.status==200){
xmlhttp.open("GET","names.txt",true);
allText = xmlhttp.responseText;
lines = xmlhttp.responseText.split("\n");
}
}
xmlhttp.send(null);
document.getElementById("myDiv").innerHTML=allText;
}
I think this is meant to change the div I have (id "myDiv") to read what is in the text file, but it does not seem to do this, no matter what I try. Any help would be appreciated - I'm still new to JavaScript and Ajax.

Use Firebug or Chrome's developer tools to make sure that the AJAX call is returning the correct text.
Is names.txt in the same directory as the HTML page?

How can I open a JSON file in JavaScript without jQuery?

I am writing some code in JavaScript. In this code i want to read a json file. This file will be loaded from an URL.
How can I get the contains of this JSON file in an object in JavaScript?
This is for example my JSON file located at ../json/main.json:
{"mainStore":[{vehicle:'1',description:'nothing to say'},{vehicle:'2',description:'nothing to say'},{vehicle:'3',description:'nothing to say'}]}
and i want to use it in my table.js file like this:
for (var i in mainStore)
{
document.write('<tr class="columnHeaders">');
document.write('<td >'+ mainStore[i]['vehicle'] + '</td>');
document.write('<td >'+ mainStore[i]['description'] + '</td>');
document.write('</tr>');
}

Here's an example that doesn't require jQuery:
function loadJSON(path, success, error)
{
var xhr = new XMLHttpRequest();
xhr.onreadystatechange = function()
{
if (xhr.readyState === XMLHttpRequest.DONE) {
if (xhr.status === 200) {
if (success)
success(JSON.parse(xhr.responseText));
} else {
if (error)
error(xhr);
}
}
};
xhr.open("GET", path, true);
xhr.send();
}
Call it as:
loadJSON('my-file.json',
function(data) { console.log(data); },
function(xhr) { console.error(xhr); }
);

XHR can be used to open files, but then you're basically making it hard on yourself because jQuery makes this a lot easier for you. $.getJSON() makes this so easy to do. I'd rather want to call a single line than trying to get a whole code block working, but that's up to you...
Why i dont want to use jQuery is because the person i am working for doesn't want it because he is afraid of the speed of the script.
If he can't properly profile native VS jQuery, he shouldn't even be programming native code.
Being afraid means he doesn't know what he is doing. If you plan to go for performance, you actually need to know how to see how to make certain pieces of code faster. If you are only just thinking that jQuery is slow, then you are walking into the wrong roads...

JSON has nothing to do with jQuery.
There is nothing wrong with the code you have now.
To store the variable mainStore, it is a variable in that json.
You should store that json to a variable:
var myJSON = {"mainStore":[{vehicle:'1',description:'nothing to say'},{vehicle:'2',description:'nothing to say'},{vehicle:'3',description:'nothing to say'}]};
var mainStore = myJSON.mainStore;
//.. rest of your code.

I understand that by "reading a json file" you mean making the request to the url that returns json content. If so, then can you explain why you don't want to use jQuery for this purpose? It has $.ajax function that is perfectly suitable for this and covers the browsers' differences.
If you want to read the file then you have to do it server-side, e.g. php and provide it somehow to the dom (there are different methods) so js can use it. Reading file from disk with js is not possible.

function loadDoc() {
const xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function () {
if (this.readyState == 4 && this.status == 200) {
console.log(xhttp.responseText)
}
};
xhttp.open("GET", "./user.json");
xhttp.send();
}
Naming using the linux filename structure
You can store the responseText to a variable or whatever you want to do with it

How to read a text file from server using JavaScript?

On the server, there is a text file. Using JavaScript on the client, I want to be able to read this file and process it. The format of the file on the server cannot be changed.
How can I get the contents of the file into JavaScript variables, so I can do this processing? The size of the file can be up to 3.5 MB, but it could easily be processed in chunks of, say, 100 lines (1 line is 50-100 chars).
None of the contents of the file should be visible to the user; he will see the results of the processing of the data in the file.

You can use hidden frame, load the file in there and parse its contents.
HTML:
<iframe id="frmFile" src="test.txt" onload="LoadFile();" style="display: none;"></iframe>
JavaScript:
<script type="text/javascript">
function LoadFile() {
var oFrame = document.getElementById("frmFile");
var strRawContents = oFrame.contentWindow.document.body.childNodes[0].innerHTML;
while (strRawContents.indexOf("\r") >= 0)
strRawContents = strRawContents.replace("\r", "");
var arrLines = strRawContents.split("\n");
alert("File " + oFrame.src + " has " + arrLines.length + " lines");
for (var i = 0; i < arrLines.length; i++) {
var curLine = arrLines[i];
alert("Line #" + (i + 1) + " is: '" + curLine + "'");
}
}
</script>
Note: in order for this to work in Chrome browser, you should start it with the --allow-file-access-from-files flag. credit.

Loading that giant blob of data is not a great plan, but if you must, here's the outline of how you might do it using jQuery's $.ajax() function.
<html><head>
<script src="jquery.js"></script>
<script>
getTxt = function (){
$.ajax({
url:'text.txt',
success: function (data){
//parse your data here
//you can split into lines using data.split('\n')
//an use regex functions to effectively parse it
}
});
}
</script>
</head><body>
<button type="button" id="btnGetTxt" onclick="getTxt()">Get Text</button>
</body></html>

You need to use Ajax, which is basically sending a request to the server, then getting a JSON object, which you convert to a JavaScript object.
Check this:
http://www.w3schools.com/ajax/tryit.asp?filename=tryajax_first
If you are using jQuery library, it can be even easier:
http://api.jquery.com/jQuery.ajax/
Having said this, I highly recommend you don't download a file of 3.5MB into JS! It is not a good idea. Do the processing on your server, then return the data after processing. Then if you want to get a new data, send a new Ajax request, process the request on server, then return the new data.
Hope that helps.

I used Rafid's suggestion of using AJAX.
This worked for me:
var url = "http://www.example.com/file.json";
var jsonFile = new XMLHttpRequest();
jsonFile.open("GET",url,true);
jsonFile.send();
jsonFile.onreadystatechange = function() {
if (jsonFile.readyState== 4 && jsonFile.status == 200) {
document.getElementById("id-of-element").innerHTML = jsonFile.responseText;
}
}
I basically(almost literally) copied this code from http://www.w3schools.com/ajax/tryit.asp?filename=tryajax_get2 so credit to them for everything.
I dont have much knowledge of how this works but you don't have to know how your brakes work to use them ;)
Hope this helps!

It looks like XMLHttpRequest has been replaced by the Fetch API. Google published a good introduction that includes this example doing what you want:
fetch('./api/some.json')
.then(
function(response) {
if (response.status !== 200) {
console.log('Looks like there was a problem. Status Code: ' +
response.status);
return;
}
// Examine the text in the response
response.json().then(function(data) {
console.log(data);
});
}
)
.catch(function(err) {
console.log('Fetch Error :-S', err);
});
However, you probably want to call response.text() instead of response.json().

Just a small point, I see some of the answers using innerhtml. I have toyed with a similar idea but decided not too, In the latest version react version the same process is now called dangerouslyinnerhtml, as you are giving your client a way into your OS by presenting html in the app. This could lead to various attacks as well as SQL injection attempts

You need to check for status 0 (as when loading files locally with XMLHttpRequest, you don't get a status and if it is from web server it returns the status)
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);
}
For device file readuing use this:
readTextFile("file:///C:/your/path/to/file.txt");
For file reading from server use:
readTextFile("http://test/file.txt");

I really think your going about this in the wrong manner. Trying to download and parse a +3Mb text file is complete insanity. Why not parse the file on the server side, storing the results viva an ORM to a database(your choice, SQL is good but it also depends on the content key-value data works better on something like CouchDB) then use ajax to parse data on the client end.
Plus, an even better idea would to skip the text file entirely for even better performance if at all possible.