[javascript] Check if a file exists locally using JavaScript only

I want to check if a file exists locally, where the HTML file is located. It has to be JavaScript. JavaScript will never be disabled. jQuery is not good but can do.

By the way, I am making a titanium app for Mac so I am looking for a way of protecting my files from people who click "show package contents".

An alternative: you can use a "hidden" applet element which implements this exist-check using a privileged action object and override your run method by:

File file = new File(yourPath);
return file.exists();

If you want to check if file exists using javascript then no, as far as I know, javascript has no access to file system due to security reasons.. But as for me it is not clear enough what are you trying to do..

Fortunately, it's not possible (for security reasons) to access client-side filesystem with standard JS. Some proprietary solutions exist though (like Microsoft's IE-only ActiveX component).

You can use this

function LinkCheck(url)
{
    var http = new XMLHttpRequest();
    http.open('HEAD', url, false);
    http.send();
    return http.status!=404;
}

Since 'Kranu' helpfully advises 'The only interaction with the filesystem is with loading js files . . .', that suggests doing so with error checking would at least tell you if the file does not exist - which may be sufficient for your purposes?

From a local machine, you can check whether a file does not exist by attempting to load it as an external script then checking for an error. For example:

<span>File exists? </span>
<SCRIPT>
    function get_error(x){
        document.getElementsByTagName('span')[0].innerHTML+=x+" does not exist.";
    }
    url="   (put your path/file name in here)    ";
    url+="?"+new Date().getTime()+Math.floor(Math.random()*1000000);
    var el=document.createElement('script');
    el.id="123";
    el.onerror=function(){if(el.onerror)get_error(this.id)}
    el.src=url;
    document.body.appendChild(el);
</SCRIPT>

Some notes...

• append some random data to the file name (url+="?"+new Date etc) so that the browser cache doesn't serve an old result.
• set a unique element id (el.id=) if you're using this in a loop, so that the get_error function can reference the correct item.
• setting the onerror (el.onerror=function) line is a tad complex because one needs it to call the get_error function AND pass el.id - if just a normal reference to the function (eg: el.onerror=get_error) were set, then no el.id parameter could be passed.
• remember that this only checks if a file does not exist.

One way I've found to do this is to create an img tag and set the src attribute to the file you are looking for. The onload or onerror of the img element will fire based on whether the file exists. You can't load any data using this method, but you can determine if a particular file exists or not.

Javascript cannot access the filesystem and check for existence. The only interaction with the filesystem is with loading js files and images (png/gif/etc).

Javascript is not the task for this

Try this:

window.onclick=(function(){
  try {
    var file = window.open("file://mnt/sdcard/download/Click.ogg");
    setTimeout('file.close()', 100);
    setTimeout("alert('Audio file found. Have a nice day!');", 101);
  } catch(err) {
    var wantstodl=confirm("Warning:\n the file, Click.ogg is not found.\n do you want to download it?\n "+err.message);
    if (wantstodl) {
      window.open("https://www.dropbox.com/s/qs9v6g2vru32xoe/Click.ogg?dl=1"); //downloads the audio file
    }
  }
});

No need for an external library if you use Nodejs all you need to do is import the file system module. feel free to edit the code below: const fs = require('fs')

const path = './file.txt'

fs.access(path, fs.F_OK, (err) => {
  if (err) {
    console.error(err)
    return
  }

  //file exists
})