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; } ?>Checking for Undefined in Javascript - Stack Overflow

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    Checking for Undefined in Javascript - Stack Overflow

    programmeradmin4浏览0评论

    I was following the below logic to check if a variable is undefined or not:

     if (variable==undefined){
////implementation
}

    But found that for some cases it did not function as expected. So, tried this approach, 

    if(typeof(variable) == "undefined"){
/////implementation
}

    So which one is most reliable?

    I was following the below logic to check if a variable is undefined or not:

     if (variable==undefined){
////implementation
}

    But found that for some cases it did not function as expected. So, tried this approach, 

    if(typeof(variable) == "undefined"){
/////implementation
}

    So which one is most reliable?

    • javascript
    • undefined
    Share Improve this question asked Jun 20, 2011 at 5:22 RK-RK- 12.2k23 gold badges93 silver badges157 bronze badges 3
    • 1 see the questions under the Related section on the right side of the page. – Anurag Commented Jun 20, 2011 at 5:26
    • possible duplicate of Detecting an undefined object property in JavaScript – Asaph Commented Jun 20, 2011 at 5:27
    • SO search javascript undefined check: 3745 results. – KooiInc Commented Jun 20, 2011 at 5:27
    Add a ment  | 

    2 Answers 2

    Reset to default 6

    Your second way is the most reliable but you don't need the parenthesis for the typeof operator. See this question.

    if (variableName){
////implementation
}

    this way is more use full than second option

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