is it possible to read a file using javascript?

Question

Hi all i just want to know if we can read a file using javascript like

what we do

fp=("r","path")

like that is it possible?

• user447356: File from server or from client?
• Free Consulting: It depends on execution environment (there are even ones with this ugly syntax, Opera's Unite runtime)
• NG.: possible duplicate of Read txt file using Javascript

Answer 1

No, that's not possible in a browser. Javascript runs in a sandboxed environment and doesn't have access to the file system. You might need to special plugins to be installed on the client browser in order to access his file system.

• T.J. Crowder: Some browsers support the File API, which allows the user to explicitly grant permission to the browser to read a local file; see my answer for details.

Answer 2

Yes, this is possible, even in some browsers.

Reading a local file, from a browser

If the browser supports the new File API, you can read any file the user gives you permission to read via an input[type=file] element. Specification | Example here on StackOverflow

Read a server file, from a browser

This can be done on all major browsers using "ajax", more specifically the XMLHttpRequest object. It's made a lot easier by libraries like jQuery, Prototype, YUI, Closure, or any of several others.

On a server, workstation, etc. (not in a browser)

You'll need an environment that provides file reading, such as NodeJS.

• Free Consulting: actually, XHR reads entity (in HTTP terms), not exactly a file (while server reads actual file)
• T.J. Crowder: @Worm: Yes, of course, but the point being that if you have a file on the server, you can serve it up via HTTP and read it via XHR.
• Free Consulting: Key is have to serve, just having a file somewhere is not enough

Answer 3

Firstly I think its not a good idea to read a file locally with JavaScript. I recommend first upload it to the server and then perform the reading.

Having said that it is possible, but you restricted by what you can do.

Im assuming its a local file on the user machine, otherwise AJAX would achieve this for a server read.

It might be possible through

1. Windows Script Host Object Model(WScript.Shell) and when granted Prompt or Enable access to ActiveX the browser has elevated privileges (Enable through Tools> Internet Options> Security> Custom Level ...> Set Active X settings to prompt). If this is still to difficult, user could download something thats installed and then does the reading through Shell Scripting! Disclaimer: Note I do not recommend this approach. Its not active for a reason and its so DIRTY (I feel dirty)!

2. Cookies might also be worth considering. If you can store the information in a cookie the JavaScript would be able to read, write and update it.

   Found this code from http://www.quirksmode.org/js/cookies.html scroll right to the bottom for the example.

   function createCookie(name,value,days) {
   if (days) {
    var date = new Date();
    date.setTime(date.getTime()+(days*24*60*60*1000));
    var expires = "; expires="+date.toGMTString();
   }
   else var expires = "";
   document.cookie = name+"="+value+expires+"; path=/";
   

   }

   function readCookie(name) {
    var nameEQ = name + "=";
    var ca = document.cookie.split(';');
    for(var i=0;i < ca.length;i++) {
    var c = ca[i];
    while (c.charAt(0)==' ') c = c.substring(1,c.length);
    if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);
    }
    return null;
   }
   function eraseCookie(name) {
    createCookie(name,"",-1);
   }
   

Answer 4

Reading from client: how to read a text file using Javascript

Reading from server: jquery - Read a text file?

Answer 5

Reading client files in javascript is possible with the new File API available in modern browsers. Check this site and its code: http://www.readfileonline.com/

Answer 6

You can but then you have to use AJAX, which is Javascript for server side jobs.

• user447356: AJAX is not "javscript for server side jobs". One good and correct definition is group of interrelated web development techniques used on the client-side to create interactive web applications (Source: Wikipedia) BTW the downvote is not mine.