onSubmit check file upload type?

On my page I have a bunch of file upload fields (all with name="files[]" so it can be processed as a PHP array).

They are all located in one of two divs, lets call them 'div1' and 'div2'.

How can I use javascript so that onSubmit, it checks the file types and all the fil开发者_运维问答es in div1 can only be 'pdf', and all the files in div2' can only be 'pdf' or 'doc'?

A simple alert popup box will do (ie. "Files can only be pdf")

Any suggestions?

****************UPDATE*******************

Made a more relevant question: Add a filetype validation to phpmailer?

---

You can make this:

HTML:

<form method="post" enctype="multipart/form-data" name="form">

<input type="file" name="file" /><br />
<input type="file" name="file" />
<input type="submit" />
</form>

JavaScript:

   var fileInput = document.getElementsByName("file");
   for(var i = 0, len = fileInput.length; i < len; i++) {
    fileInput[i].addEventListener('change', 
        function(e) {
            if(this.files[0].name.match(/\.pdf$/) == null) {
                alert('Files can only be PDF.');
                return;
            }
        },
        false
    );
 }

---

File upload elements are heavily protected in browsers, and JS has minimal access to its contents. Anything dealing with the file itself is pretty much locked off, as any hole in the system could allow a malicious site to steal files from the user's computer.

The easiest workaround is to just put up a small note next to the fields say "PDF Only!" and then use a server-side script to confirm that it is a pdf.

---

You can address the form element and read the name attribute, then you get the file name and can work with the file extension.

But this may only be used to make it easier to the user - so you can detect wrong file types before the uploading process.

It is NOT a protection in any way.

You can also pass the filestypes expected to the dialog itself. Most file managers and browsers respect it and display only the files of the type you want to choose, but the user can click a dropdown and select "view all files" and pic whatever files he/she want.

This is done with the accept attribute.

If you want to help the user choosing the right file both methods above are appropriate and I would even use them together.

If you want to protect your service from wrong filetypes, you have to evaluate the files server side. A file extension checking is not appropriate, there are php functions available to determine the real mimetype of a file.

---

You can check on submit for each file upload using this code:

var parts = document.getElementById('myFileField').value.split('.');
if (parts[parts.length-1] != 'pdf') {
    alert('Invalid extension. Needs to be PDF.');
}

Incorporating work by The Mask,

var fileInputs = document.getElementsByName("files[]");
for (var ele in fileInputs) {
    if (ele.parentNode.id = 'div1') {
        var parts = ele.value.split('.');
        if (parts[parts.length-1] != 'pdf') {
            alert('Invalid extension: "' + ele.value + '". Needs to be PDF.');
        }
    }
    else if (ele.parentNode.id = 'div2') {
        var parts = ele.value.split('.');
        if (parts[parts.length-1] != 'pdf' && parts[parts.length-1] != 'doc') {
            alert('Invalid extension: "' + ele.value + '". Needs to be PDF or DOC.');
        }
    }
}