te')); return $arr; } /* 遍历用户所有主题 * @param $uid 用户ID * @param int $page 页数 * @param int $pagesize 每页记录条数 * @param bool $desc 排序方式 TRUE降序 FALSE升序 * @param string $key 返回的数组用那一列的值作为 key * @param array $col 查询哪些列 */ function thread_tid_find_by_uid($uid, $page = 1, $pagesize = 1000, $desc = TRUE, $key = 'tid', $col = array()) { if (empty($uid)) return array(); $orderby = TRUE == $desc ? -1 : 1; $arr = thread_tid__find($cond = array('uid' => $uid), array('tid' => $orderby), $page, $pagesize, $key, $col); return $arr; } // 遍历栏目下tid 支持数组 $fid = array(1,2,3) function thread_tid_find_by_fid($fid, $page = 1, $pagesize = 1000, $desc = TRUE) { if (empty($fid)) return array(); $orderby = TRUE == $desc ? -1 : 1; $arr = thread_tid__find($cond = array('fid' => $fid), array('tid' => $orderby), $page, $pagesize, 'tid', array('tid', 'verify_date')); return $arr; } function thread_tid_delete($tid) { if (empty($tid)) return FALSE; $r = thread_tid__delete(array('tid' => $tid)); return $r; } function thread_tid_count() { $n = thread_tid__count(); return $n; } // 统计用户主题数 大数量下严谨使用非主键统计 function thread_uid_count($uid) { $n = thread_tid__count(array('uid' => $uid)); return $n; } // 统计栏目主题数 大数量下严谨使用非主键统计 function thread_fid_count($fid) { $n = thread_tid__count(array('fid' => $fid)); return $n; } ?>javascript - How to disable submit button until file is selected - Stack Overflow

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    javascript - How to disable submit button until file is selected - Stack Overflow

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    I have an HTML file upload page and I need the submit button to be disabled until a file is selected. Then the submit button will be enabled and the user can upload. I assume I can use jQuery code to query the file upload field's value to see whether a file has been selected to upload. And I assume I can check that whenever focus has left the file upload field. My concern is that some browsers might act funny with this and then my users can't upload any files.

    Is there a safe way to do this, preferably using jQuery, where I won't be in danger of having some users unable to upload?

    I have an HTML file upload page and I need the submit button to be disabled until a file is selected. Then the submit button will be enabled and the user can upload. I assume I can use jQuery code to query the file upload field's value to see whether a file has been selected to upload. And I assume I can check that whenever focus has left the file upload field. My concern is that some browsers might act funny with this and then my users can't upload any files.

    Is there a safe way to do this, preferably using jQuery, where I won't be in danger of having some users unable to upload?

    • javascript
    • jquery
    • forms
    • file-upload
    • jquery-validate
    Share Improve this question asked Dec 12, 2010 at 9:38 at.at. 52.6k105 gold badges303 silver badges470 bronze badges
    Add a ment  | 

    3 Answers 3

    Reset to default 9

    This jQuery should work, and is tied to the file input's change() event. This code also applies the disabled attribute so, in the event the user has JavaScript disabled, it shouldn't prevent the form being used:

    $(document).ready(
    function(){
        $('input:submit').attr('disabled',true);
        $('input:file').change(
            function(){
                if ($(this).val()){
                    $('input:submit').removeAttr('disabled'); 
                }
                else {
                    $('input:submit').attr('disabled',true);
                }
            });
    });

    JS Fiddle demo.

    A simpler way is to check the file field when the user actually submits the form... that way you won't have to look for form changes.

    $(function() {
   $('form').submit(function() {
      if(!$("form input[type=file]").val()) {
         alert('You must select a file!');
         return false;
      }
   });
});

    This code is Unobtrusive JavaScript and it won't mess up the form if the user does not support JS.

    David Thomas's code can be set for button ID:

    <script type="text/javascript">
    $(document).ready(function () {
        $('#<%=btInsert.ClientID %>').attr('disabled', true);
        $('input:file').change(
            function () {
                if ($(this).val()) {
                    $('#<%=btInsert.ClientID %>').removeAttr('disabled');
                }
                else {
                    $('#<%=btInsert.ClientID %>').attr('disabled', true);
                }
            });
    });
</script>

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