how to determine type of file using javascript when onload?

Question

I have certain uploaded file code as following:

<script>
var input_file = document.getElementById('txt_list');
input_file.onchange = function() {
           var file = this.files[0];
           var reader = new FileReader();
           reader.onload = function(ev) {
                //myProcesses
           };
           reader.readAsText(file);
        };
</script>

How can I add new function to determine the type of uploaded file either txt, gif, etc? and if i have to validate it, what am i supposed to do then? Thanks in advance

possible duplicate of How can i get file extensions with javascript? — Aleks G
– Aleks G, Commented Oct 25, 2012 at 9:27

Community · Accepted Answer · 2017-05-23 10:34:54Z

2

return (/[.]/.exec(filename)) ? /[^.]+$/.exec(filename) : undefined;

or

return filename.split('.').pop();

please refer this link for more details -LINK

if u need a txt file only

save it to a variable and use a if else statement to verify it

var file=file.split('.').pop();


if (type=='txt'){
//do something
}else{
//do something
}

edited May 23, 2017 at 10:34

CommunityBot

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answered Oct 25, 2012 at 5:26

Ghostman

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1 Comment

Ghostman Over a year ago

use this var file=file.split('.').pop(); see my updated answer

Buzz · Accepted Answer · 2012-10-25 05:30:57Z

2

split the filename then second part will give you file extension

 return file .split('.').pop();

so if file is name.txt this will return txt

edit-

if you only have to check the filetype

var filetype=file.split('.').pop();
if(filetype!="txt"){
return false;
}

edited Oct 25, 2012 at 5:30

answered Oct 25, 2012 at 5:21

Buzz

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2 Comments

Buzz Over a year ago

var file = this.files[0]; return file .split('.').pop();

Doni Andri Cahyono Over a year ago

ok thanks. And maybe my next question, if it's not too much, what if I have to validate it? I need .txt only, for instance.

Musa · Accepted Answer · 2012-10-25 05:29:15Z

1

You could use File.type to determine the mime type and check it against valid mime types.

answered Oct 25, 2012 at 5:29

Musa

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