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simple javascript/ajax call - does not return status

The following code produces nothing on the html page, it seems to break down on 'status':
var get_json_file = new XMLHttpRequest();
get_json_file.open("GET", "/Users/files/Documents/time.json", true);
**document.write(get_json_file.status);**
keep in mind, that I am on a Mac, so there is no C: drive....however, this line of code does work fine:
document.write(get_json_file.readyState);
I just want to know that I was able to successfully find my json file. Perhaps, I should ask, what should I be looking for to achieve what I want ?

Another basic question about AJAX. I suggest you to read the MDN article about using XMLHttpRequest. You can't access the 'status' property until it is ready, and you haven't even called the 'send()' method, which performs the actual request. You can't have a status without making an HTTP request first. Learn how AJAX works before trying to use it. Explaining it all would be too long and this is not the place.

You can only get the status when the ajax has finished. That is, when the page was loaded, or a 404 was returned.
Because you're trying to call status straight after the request was sent (or not sent, read the P.S), you're getting nothing.
You need to make an async call, to check that status only when the request finishes:
get_json_file.onreadystatechange = function (){
if (get_json_file.readyState==4 && get_json_file.status==200)
{
alert('success');
}
}
read more at http://www.w3schools.com/ajax/ajax_xmlhttprequest_onreadystatechange.asp
P.S as noted by #Oscar, you're missing the send().
If you want to try a synchronous approach, which would stop the code from running until a response is returned, you can try:
var get_json_file = new XMLHttpRequest();
get_json_file.open("GET", "/Users/files/Documents/time.json", false);
//notice we set async to false (developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest)
get_json_file.send(); //will wait for a response
document.write(get_json_file.status);
//(Credit: orginial asker)

Because of security issues you are not allowed to send requests to files on the local system, but what you could do is look into the fileReader API. (more info here)
<sidenote>
The reason that the readyState works and not status is because by defualt
readyState has a value of 0 and status has no value so it would be undefined.
</sidenote>

in my ubuntu, the path will be prefixed with file:///
i think your json file path should have file:///Users/files/Documents/time.json, because mac and ubuntu based on unix
and then you can check ajax status using #TastySpaceApple answer
if you using google chrome, don't forget to launch it with -–allow-file-access-from-files command, because google chrome not load local file by default due to security reason

reading server file with javascript

I have a html page using javascript that gives the user the option to read and use his own text files from his PC. But I want to have an example file on the server that the user can open via a click on a button.
I have no idea what is the best way to open a server file. I googled a bit. (I'm new to html and javascript, so maybe my understanding of the following is incorrect!). I found that javascript is client based and it is not very straightforward to open a server file. It looks like it is easiest to use an iframe (?).
So I'm trying (first test is simply to open it onload of the webpage) the following. With kgr.bss on the same directory on the server as my html page:
<IFRAME SRC="kgr.bss" ID="myframe" onLoad="readFile();"> </IFRAME>
and (with file_inhoud, lines defined elsewhere)
function readFile() {
func="readFile=";
debug2("0");
var x=document.getElementById("myframe");
debug2("1");
var doc = x.contentDocument ? x.contentDocument : (x.contentWindow.document || x.document);
debug2("1a"+doc);
var file_inhoud=doc.document.body;
debug2("2:");
lines = file_inhoud.split("\n");
debug2("3");
fileloaded();
debug2("4");
}
Debug function shows:
readFile=0//readFile=1//readFile=1a[object HTMLDocument]//
So statement that stops the program is:
var file_inhoud=doc.document.body;
What is wrong? What is correct (or best) way to read this file?
Note: I see that the file is read and displayed in the frame.
Thanks!

Your best bet, since the file is on your server is to retrieve it via "ajax". This stands for Asynchronous JavaScript And XML, but the XML part is completely optional, it can be used with all sorts of content types (including plain text). (For that matter, the asynchronous part is optional as well, but it's best to stick with that.)
Here's a basic example of requesting text file data using ajax:
function getFileFromServer(url, doneCallback) {
var xhr;
xhr = new XMLHttpRequest();
xhr.onreadystatechange = handleStateChange;
xhr.open("GET", url, true);
xhr.send();
function handleStateChange() {
if (xhr.readyState === 4) {
doneCallback(xhr.status == 200 ? xhr.responseText : null);
}
}
}
You'd call that like this:
getFileFromServer("path/to/file", function(text) {
if (text === null) {
// An error occurred
}
else {
// `text` is the file text
}
});
However, the above is somewhat simplified. It would work with modern browsers, but not some older ones, where you have to work around some issues.
Update: You said in a comment below that you're using jQuery. If so, you can use its ajax function and get the benefit of jQuery's workarounds for some browser inconsistencies:
$.ajax({
type: "GET",
url: "path/to/file",
success: function(text) {
// `text` is the file text
},
error: function() {
// An error occurred
}
});
Side note:
I found that javascript is client based...
No. This is a myth. JavaScript is just a programming language. It can be used in browsers, on servers, on your workstation, etc. In fact, JavaScript was originally developed for server-side use.
These days, the most common use (and your use-case) is indeed in web browsers, client-side, but JavaScript is not limited to the client in the general case. And it's having a major resurgence on the server and elsewhere, in fact.

The usual way to retrieve a text file (or any other server side resource) is to use AJAX. Here is an example of how you could alert the contents of a text file:
var xhr;
if (window.XMLHttpRequest) {
xhr = new XMLHttpRequest();
} else if (window.ActiveXObject) {
xhr = new ActiveXObject("Microsoft.XMLHTTP");
}
xhr.onreadystatechange = function(){alert(xhr.responseText);};
xhr.open("GET","kgr.bss"); //assuming kgr.bss is plaintext
xhr.send();
The problem with your ultimate goal however is that it has traditionally not been possible to use javascript to access the client file system. However, the new HTML5 file API is changing this. You can read up on it here.

Access-Control-Allow-Origin error when trying to get resources from site in same domain?

I'm merely trying to grab the html from one of my other sites on the server and print it on the current site. Here's basically what I'm doing:
// The object
var xmlhttp = new XMLHttpRequest();
// When a button is pressed, we get the html
function printJSON(action)
{
otherURL = "http://www.my.domain.com/other.php?action=" +action;
xmlhttp.open('GET',otherURL,true);
xmlhttp.send();
}
// and then print it in this div
xmlhttp.onreadystatechange = function
{
if(xmlhttp.readyState == 4 && xmlhttp.status == 200)
{
$('JSON_output').innerHTML = xmlhttp.responseText;
}
}
and the error I'm receiving is:
XMLHttpRequest cannot load http://www.my.domain.com/other.php?action=SEARCH. Origin http://my.domain.com is not allowed by Access-Control-Allow-Origin.
Which seems strange, because this is one site on the server trying to access another site right within the same folder. Is there something I need to adjust on my server? An attribute in xmlhttp I need to set?
Cheers!

http://www.my.domain.com and http://my.domain.com are two different domains (note the www) according to the JavaScript same-origin policy.
If www.my.domain.com and my.domain.com point to the same place, the simplest solution would be to make otherURL relative; start it with "/other.php?action="; that way, it will always be on the same domain as your page.
If they do not, point to the same place, there is a much more complicated solution involving your server outputting additional headers called Cross Origin Resource Sharing; here's an overview.

Ajax call from Bookmarklet

I am trying to create a bookmarklet that, upon clicking, would request some information from the user (a url and a couple other fields in this case) and then send that data to a php page on my server and then display the result.
I would like to do an Ajax call for this so that I don't actually redirect to the new page, just get the data but I assume I would run into the "Same Origin Policy" limitation of Ajax.... is there any known way of basically doing the same thing?
Also, what would be the best way to pass the parameters? I already have a mechanism in place to recieve the parameters as a post message from a form...is there any way I could just reuse this?

You can set a bookmarklet by create a bookmark and add that piece of code below in location, but, according to same origin policy limitation, that will only work when the current tab is on the same location, here www.google.com.
If I've understand well your needs, that should be ok for your problem.
var request = new XMLHttpRequest();
request.open("GET", "http://www.google.com", true);
request.onreadystatechange = function() {
var done = 4, ok = 200;
if (request.readyState == done && request.status == ok) {
if (request.responseText) {
alert(request.responseText);
}
}
};
request.send(null);
I don't know if POST would work.

You won't be able to do a post, but a GET will work fine. If you're using something like jQuery, it will simply create a script tag with a src URL which would send the data you are looking to submit.
You will have to return JSON style data.
See: http://docs.jquery.com/Ajax/jQuery.getJSON
Alternatively, your bookmarklet could create an iframe on the page, and that could do you work of submitting the data (you could use post then) if you weren't looking to communicate between the iframe and the page itself, but instead just use user input to submit.

Reading from a http-get presenting in Firefox bookmarks

I'm trying to get a Firefox plugin to read data from a HTTP get, parse the results and present them as links in a bookmark-like drop-down menu.
My quesion then is: Does anyone have any sample code that will do this?

Having never developed one myself, I'm not certain how this is typically done in Firefox plugins, but since plugin scripting is JavaScript, I can probably help out with the loading part. Assuming a variable named url containing the URL you want to request:
var xmlhttp = new XMLHttpRequest();
xmlhttp.open("GET", url, true);
xmlhttp.onreadystatechange = function() {
if(this.readyState == 4) { // Done loading?
if(this.status == 200) { // Everything okay?
// read content from this.responseXML or this.responseText
} else { // Error occurred; handle it
alert("Error " + this.status + ":\n" + this.statusText);
}
}
};
xmlhttp.send(null);
A couple of notes on this code:
You may want more sophisticated status code handling. For example, 200 is not the only non-error status code. Details on status codes can be found here.
You probably want to have a timeout to handle the case where, for some reason, you don't get to readyState 4 in a reasonable amount of time.
You may want to do things when earlier readyStates are received. This page documents the readyState codes, along with other properties and methods on the XMLHttpRequest object which you may find useful.

Robert Walker did a great job of describing how to send the request. You can read more about Mozilla's xmlhttprequest here.
I would just add that the response would be found (using Robert's code) using
xmlhttp.responseText
(Edit - i didn't read closely enough, thanks Robert)
You didn't indicate exactly what the data was, although you mentioned wanting to parse links from the data. You could the xmlhttp.responseText as an xml document, parse out the links, and place it into a menulist or whatever you like.