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Thread: Image file size

  1. #1
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    Image file size

    I have a form that allows photos to be uploaded. I am using Perl to do this, and it works fine. Now I want to validate that the size of the image does not exceed a certain limit BEFORE it actually uploads. I can do that in Perl using something like the code below. But, I would rather do this in Javascript. I already have a routine that validates that the image file name does not contain embedded spaces. I would like to add this there.

    Can this be done in Javascript?

    Code:
    if ($ENV{'CONTENT_LENGTH'} > 100000) { print "SIZE EXCEEDS LIMIT!" }

  • #2
    Supreme Master coder! Old Pedant's Avatar
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    JavaScript has no ability to manipulate files in the client's computer. And, yes, that even includes reading the directory to find whether a file exists and/or finding the size of the file.

    You *CAN* do this in MSIE (only) by using an ActiveX object, but even with MSIE this is considered "unsafe scripting" and is only allowed if your site is a "trusted domain" (as specified by the browser user, not by you!) *AND* if the user allows the code to run. In short, even with MSIE it's not a viable alternative except for maybe inTRAnet situations.
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  • #3
    Kor
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    Quote Originally Posted by Old Pedant View Post
    And, yes, that even includes reading the directory to find whether a file exists
    Not really. In fact JavaScript can sense if an external file exists or not, but only after the document tries to load it.
    Code:
    <img src="moo/boo.jpg" onerror="alert('no such a folder/file found!');this.parentNode.removeChild(this)">
    It works in all the browsers I know (including IE6 ). Except that in Opera, for a reason or another, the event fires twice.

    But, indeed, JavaScript is not able to find the size of a ready for upload file.
    Last edited by Kor; 12-11-2010 at 01:44 PM.
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