file upload checking

[gryffin]

im trying to do file extension checking but its not working :(

i have the following in the head

<script language="JavaScript">
    extArray = new Array(".jpg", ".png", ".bmp");
    function LimitAttach(form, file) {
    allowSubmit = false;
    if (!file) return;
    while (file.indexOf("\\") != -1)
    file = file.slice(file.indexOf("\\") + 1);
    ext = file.slice(file.indexOf(".")).toLowerCase();
    for (var i = 0; i < extArray.length; i++) {
    if (extArray[i] == ext) { allowSubmit = true; break; }
    }
    if (allowSubmit) return true;
    else
    alert("Please only upload files that end in types:  "
    + (extArray.join("  ")) + "\nPlease select a new "
    + "file to upload and submit again.");
    return false;
    }
    //  End -->
</script>

this is the html code
the {} are things inserted via php
i believe it is something to do with the onclick

[HTML] <form name="upload" action="{THIS}" method="post" enctype="multipart/form-data">
<input type="hidden" name="MAX_FILE_SIZE" value="6510200">
<input type="hidden" name="op" value="upload" />
<input type="hidden" name="dir" value="{NEXT_DIR}" />
<table border="0" width="100%" cellpadding="1">
<tr class="task_cell">
<td width="5%" nowrap="nowrap"><b>{LOCAL}</b>&nbsp;</td>
<td width="70%"><input type="file" name="local" size="45" style="width: 90%" onchange="javascript:filename();" /></td>
<td valign="bottom" align="right"><input onclick="javascript: window.location.href = '{MULTI_UPLOAD}?dir={NEXT_DIR}';" type="button" value="{MULTIPLE}" /></td>
</tr>
<tr class="task_cell">
<td width="5%" nowrap="nowrap"><b>{UPNAME}</b>&nbsp;</td>
<td width="70%"><input type="text" name="remote" size="45" style="width: 90%" /></td>
<td align="right" valign="bottom"><input onclick="javascript: return isValid(); return LimitAttach(this.form, this.form.local.value);" type="submit" value="{UPLOAD}" /></td>
</tr>
</table>
</form>[/HTML]

if anyone knows whats wrong please help, i will even pay you if you dont need too much as my site cant survive atm without it :)

[HTML]<input onclick="javascript: return isValid(); return LimitAttach(this.form, this.form.local.value);" type="submit" value="{UPLOAD}" /> [/HTML]

is most likley where im going wrong

[acoder]

LimitAttach will never run because there is already a return when calling isValid(). Either put both in a separate function and call that or change the return into an if-else statement, so if it's valid, LimitAttach is called, e.g.[HTML]<input onclick="if (isValid()) return LimitAttach(this.form, this.form.local.value); else return false;" type="submit" value="{UPLOAD}" /> [/HTML]It's better calling this from form onsubmit rather than submit button onclick.